Zebra Troubleshooting guide

Zebra ZT420 troubleshooting guide: errors, faults and fixes

Updated 21 October 2026 · By TIMCOD maintenance technicians · Source: official Zebra documentation, ZT400 Series user guide (ZT400 Series Industrial Printer User Guide), shared by the ZT410 and ZT420 (list at the end of the page)

Request a repair Printable versionPDF · 935 KB

Phone support, repair and express exchange by TIMCOD technicians. The request form is in French.

In brief. The Zebra ZT420 is an industrial label printer in the ZT400 Series, thermal transfer or direct thermal, at 203 or 300 dpi; its maximum print width is 1,344 dots at 203 dpi and 1,984 dots at 300 dpi, about 168 mm. It is also available in an RFID version. It reports its alerts on a control display and with five lights (STATUS, PAUSE, DATA, SUPPLIES, NETWORK). According to Zebra documentation, the most common faults come from incorrectly loaded media or ribbon, a calibration that needs redoing, a dirty printhead or incorrectly set printhead pressure. This guide covers each documented alert and the official calibration, adjustment and maintenance procedures. Click a question to open its entry.

An alert is displayed or a light is on (Media Out, Ribbon Out, red STATUS…): find it in the lookup table and open the matching entry.
No alert, but the print is poor: start with calibration, then the ribbon and print quality entries (printhead cleaning, darkness, dial pressure).
The problem keeps coming back: the preventive maintenance section explains how it reduces this type of fault.

Product pages on timcod.fr (in French): Zebra ZT420 · Zebra ZT400 Series · Zebra RFID ZT400 Series

Which alert is my Zebra ZT420 showing? Lookup by message and by lights

The ZT420 reports its alerts on the control display and with five lights (STATUS, PAUSE, DATA, SUPPLIES, NETWORK). The table links each alert documented by Zebra to its cause and to the entry that resolves it.

Message or state	Lights (Zebra guide)	Likely cause	Entry
`Head Open`	STATUS solid red, PAUSE solid yellow	Printhead not fully closed or faulty head-open sensor	Head Open
`Media Out`	STATUS solid red, SUPPLIES solid red	Media missing or incorrectly loaded, sensor incorrectly positioned, media type set incorrectly	Media Out
`Media Low`	—	Media almost used up	Media Out
`Ribbon Out`	STATUS solid red, SUPPLIES flashing yellow	Ribbon missing, incorrectly loaded or not detected; threshold too high; wrong print mode	Ribbon Out
`Ribbon Not Expected (Ribbon In)`	STATUS solid yellow, SUPPLIES flashing yellow	Ribbon loaded while the printer is set to direct thermal	Ribbon in direct thermal
`Non-genuine Zebra printhead`	STATUS, PAUSE and DATA solid red	Printhead that is not a genuine Zebra part	Non-genuine printhead
`Printhead resolution unreadable`	STATUS flashing red	The printer cannot read the printhead's dpi setting	Non-genuine printhead
`Print Head Over Temperature`	STATUS solid yellow	Printhead too hot	Printhead overheating
`Alternating printhead messages`	STATUS solid yellow	Printhead cable incorrectly connected or faulty thermistor	Printhead cable or thermistor
`Print Head Under Temperature`	STATUS flashing yellow	Printhead too cold (room below 15 °C), printhead cable or thermistor	Head too cold
`Cut Error`	STATUS solid red, PAUSE solid yellow	Blade in the media path, dirty cutter or cutter sensor	Cutter error
`Network error`	NETWORK solid red	Ethernet or Wi-Fi error: printer not connected to the network	Network
`USB host port disabled`	—	USB device connected to a disabled host port	USB memory stick
`Insufficient memory`	—	Not enough memory for the function shown on the second line of the message	Memory
`RfidCountryCodeNotSelected (RFID version)`	—	No RFID country code selected	RFID settings

The lights come from the “Error Message Lookup” page of the Zebra ZT400 Series guide, supplemented by the ZT400 quick reference guide (STATUS flashing red, NETWORK light). The online table shows the display messages as images: the alert names (Head Open, Media Out, Ribbon Out…) are those of the Zebra “ZT400 Alert” help pages and of the Zebra knowledge base. For Ribbon Out, the quick reference guide and the knowledge base give SUPPLIES flashing red, and the knowledge base also gives SUPPLIES flashing red for Media Out. A dash means that the page consulted does not specify the state of the lights.

Zebra ZT420 alerts: Head Open, Media Out, Ribbon Out, causes and solutions

This section covers the alerts in the official ZT400 Series table related to the printhead, media, ribbon, temperature and memory; the non-genuine printhead, cutter, USB port and RFID alerts are covered in their own sections. For each one: the short answer, the cause, the steps to take and, where the guide provides for it, when to hand over to a technician.

Why does my Zebra ZT420 show “Head Open” when the printhead is closed?

Alert: Head Open · Lights: STATUS solid red, PAUSE solid yellow.

Short answer: According to Zebra, either the printhead is not completely closed, or the head-open sensor is malfunctioning. Close the printhead until it locks; if the alert stays on the display, the guide provides for the sensor to be replaced by a technician.

Likely cause

The “Error Message Lookup” table in the ZT400 Series guide gives two causes: a printhead that is not properly closed, or a faulty head open sensor.

Caution: Zebra warns that the printhead may be hot and can cause severe burns: let it cool before opening the printhead or touching it.

What to do

Raise the printhead release lever, then lower it until it locks the printhead in place.
Check the lights: if STATUS stays red and PAUSE yellow while the printhead is latched, the head open sensor is at fault.

When to call a technician: if the alert persists with the printhead latched, Zebra leaves replacement of the head open sensor to a service technician.

The same combination of lights (STATUS red, PAUSE yellow) also indicates a cutter error: see the cutter entry.

Sources: Error Message Lookup (opens in a new window) – Zebra ZT400 Series user guide · Performing Manual Sensor Calibration (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Alert: Head Open (opens in a new window) – Zebra help pages for ZT400 Series alerts (official documentation).

Why does my Zebra ZT420 show “Media Out” when labels are loaded?

Alert: Media Out · Lights: STATUS solid red, SUPPLIES solid red.

Short answer: The media is missing or incorrectly loaded, the media sensor is incorrectly positioned, or the printer expects separate labels when continuous media is loaded. Reload the roll, check the sensor and the MEDIA TYPE setting, then calibrate.

Likely cause

The Zebra guide gives three causes: media missing or incorrectly loaded, media sensor misaligned, printer set for non-continuous media while continuous media is loaded. The Zebra knowledge base article on ZT400 Series Media Out errors adds a printer that has not been calibrated for the loaded media.

Caution: On models fitted with a cutter, Zebra points out that the blade is sharp: do not touch it while loading. Zebra warns that the printhead may be hot and can cause severe burns: let it cool before opening the printhead or touching it.

What to do

Reload the media following the “Loading the Media” procedure: the media goes under the dancer assembly, through the media sensor, then under the printhead. Slide it in until it touches the inner wall of the sensor, then bring the media guide in until it just touches the edge of the media.
Check the position of the media sensor. The guide states that the reflective sensor works with all media types, and that the transmissive sensor should only be used for simple gap media.
In the SETTINGS menu, check MEDIA TYPE: CONTINUOUS, GAP/NOTCH or MARK. Install the intended media or adapt the setting to the media loaded.
Calibrate the printer (see the calibration entry).
Press FEED: if a single label advances each time you press it, the calibration is correct. If not, the Zebra article advises cleaning the media sensor and repeating the calibration.

The Zebra article on Media Out errors describes the SUPPLIES light flashing red, whereas the table in the guide gives SUPPLIES solid red. With MEDIA TYPE set to CONTINUOUS, the label format must include a label length (^LL in ZPL). If the problem persists, Zebra advises printing a sensor profile (SENSOR PROFILE) and sending it to technical support. The “Media Low” alert only means that the media is almost used up: load more media.

Sources: Error Message Lookup (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Series Printers: Solving Media Out Errors and Calibrating the Printer – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Performing Manual Sensor Calibration (opens in a new window) · Video: Fix Media Out Error Code on ZT410 and ZT420 Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Error Message Lookup — MEDIA OUT (opens in a new window) · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version · ZT400 Alert: MediaLow (opens in a new window) – Zebra help pages for ZT400 Series alerts · ZT400 Alert: Media Out (opens in a new window) – Zebra help pages for ZT400 Series alerts (official documentation).

Why does my Zebra ZT420 show “Ribbon Out” when the ribbon is installed?

Alert: Ribbon Out · Lights: STATUS solid red, SUPPLIES flashing (yellow according to the table in the guide, red according to the quick reference guide and the Zebra knowledge base).

Short answer: In thermal transfer mode, the printer does not detect the ribbon: ribbon missing or incorrectly loaded, sensor blocked by the media, detection threshold too high, or direct thermal labels with the printer set to thermal transfer. Reload the ribbon, then calibrate the sensors.

Likely cause

The error message table lists: ribbon missing, incorrectly loaded or not detected; media blocking the ribbon sensor; ribbon loaded correctly but the ribbon out threshold set too high; direct thermal media used while the printer is set to thermal transfer.

What to do

Reload the ribbon (“Loading the Ribbon” procedure): push the roll fully onto the ribbon supply spindle so that it sits over the reflective plate, feed the ribbon under the printhead keeping it as far back as possible, then wind it onto the ribbon take-up spindle.
Calibrate the ribbon and media sensors (see the calibration entry).
If the ribbon is loaded correctly, print a sensor profile (PRINT INFORMATION > SENSOR PROFILE, or FEED + CANCEL at power-up). If the ribbon out threshold appears above the detected ribbon line, calibrate again or reload the defaults (LOAD DEFAULTS).
If your labels are direct thermal (a black mark appears when you scratch the surface with a fingernail), set PRINT METHOD to DIRECT THERMAL in the SETTINGS menu, as well as in the driver and the label software.

The opposite case: if the printer does not stop at the end of the ribbon, the “Ribbon Issues” table says that it was calibrated without ribbon or with incorrectly loaded ribbon. Load the ribbon so that the sensor can see it (under the printhead, it must go all the way in, near the rear wall of the printer), then recalibrate. With white ribbon, the Zebra ribbon article asks you to follow the loading diagram stuck on the wall of the compartment: incorrect loading causes false ribbon out alerts and wrinkling.

Sources: Error Message Lookup (opens in a new window) – Zebra ZT400 Series user guide · Troubleshooting Ribbon Out Error on ZT410 and ZT420 Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Error Message Lookup — RIBBON OUT (opens in a new window) · Resolving Ribbon Issues on ZT400 Series Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Ribbon Issues (opens in a new window) · Ribbon Issues (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Series Quick Reference Guide (P1060608-004) (opens in a new window) – Zebra ZT400 Series quick reference guide · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version (official documentation).

Why does my Zebra ZT420 show “Ribbon Not Expected” (ribbon present) in direct thermal mode?

Alert: Ribbon Not Expected (Ribbon In) · Lights: STATUS solid yellow, SUPPLIES flashing yellow.

Short answer: A ribbon is loaded while the printer is set to direct thermal. With direct thermal labels, remove the ribbon; with thermal transfer labels, set PRINT METHOD to THERMAL TRANS.

Likely cause

The Zebra table attributes this warning to a ribbon loaded while the printer is in direct thermal mode. The guide states that this message does not affect printing.

What to do

Do the scratch test: quickly scratch the label surface with your fingernail. A black mark indicates direct thermal media, which does not need a ribbon.
Direct thermal media: remove the ribbon.
Thermal transfer media: set PRINT METHOD to THERMAL TRANS (SETTINGS menu), as well as in the driver and the label software.
If the alert is still displayed without ribbon, the Zebra article advises cleaning the ribbon sensor, then manually calibrating the media and ribbon sensors (see the calibration entry).

The Zebra article on ZT400 Series ribbon calls this alert “Ribbon In” or “Ribbon Not Expected” and also suggests reloading the factory defaults to let the printer recalibrate.

Sources: Error Message Lookup (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Alert: Ribbon Not Expected (opens in a new window) – Zebra help pages for ZT400 Series alerts · Resolving Ribbon Issues on ZT400 Series Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Ribbon Issues (opens in a new window) · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version (official documentation).

Why does my Zebra ZT420 stop with the “Print Head Over Temperature” alert?

Alert: Print Head Over Temperature · Light: STATUS solid yellow.

Short answer: The printhead is too hot: the printer stops printing to avoid damaging it. Let it cool down and printing resumes by itself; if the alert comes back, move the printer or reduce the print speed.

Likely cause

Printhead temperature too high. The Zebra help page for this alert states that printing is stopped to prevent the printhead from overheating and being damaged.

Caution: Zebra warns that the printhead can cause severe burns: let it cool before touching it.

What to do

Let the printer cool down: printing resumes automatically.
If the alert persists, install the printer in a different location or choose a slower print speed (PRINT SPEED, SETTINGS menu).

Sources: Error Message Lookup (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Alert: Print Head Over Temperature (opens in a new window) – Zebra help pages for ZT400 Series alerts (official documentation).

Why does my Zebra ZT420 show “Print Head Under Temperature” with the STATUS light flashing yellow?

Alert: Print Head Under Temperature · Light: STATUS flashing yellow.

Short answer: The printhead is approaching its lower temperature limit. Keep printing: the printhead warms up and the alert should clear. If it persists, install the printer in a warmer place.

Likely cause

Printhead too cold. The Zebra help page for this alert states that the printhead is operating in an environment below 15 °C (59 °F), which can degrade print quality. For the same light, the table in the guide also lists a printhead data cable that is not properly connected or a faulty thermistor.

What to do

Keep printing: the printhead warms up, the alert should clear and print quality should improve.
If the alert persists, move the printer to a warmer place.
If the printer is already in a room at a normal temperature, the printhead cable or its thermistor may be at fault (see the printhead cable or thermistor entry).

When to call a technician: if the alert persists in a room at a normal temperature, Zebra leaves reconnecting the printhead data cable, or replacing the printhead if the thermistor is faulty, to a technician.

According to the quick reference guide, STATUS flashing yellow more broadly indicates a printhead, power supply or main logic board outside its temperature range (too cold or too hot).

Sources: Error Message Lookup (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Alert: Print Head Under Temperature (opens in a new window) – Zebra help pages for ZT400 Series alerts · ZT400 Series Quick Reference Guide (P1060608-004) (opens in a new window) – Zebra ZT400 Series quick reference guide (official documentation).

Why does my Zebra ZT420 report a lack of memory?

Insufficient memory alert: the second line of the message shows the function concerned (no light specified in the Zebra table).

Short answer: The available memory is not enough for the requested function, or the data is being sent to a device that is missing or unavailable. Simplify the label format or the settings, for example by setting the print width to the actual width of the label.

Likely cause

The Zebra table gives two causes: not enough memory to carry out the requested function, or data sent to a device that is not installed or not available.

What to do

Free up memory by adjusting the label format or the printer settings: in particular, set PRINT WIDTH (SETTINGS menu) to the actual width of the label.
Check that the device the data is intended for is installed and available.

When to call a technician: if the lack of memory persists, Zebra asks you to call a service technician.

The guide points out that a print width set too wide wastes formatting memory and can cause printing on the platen roller.

Sources: Error Message Lookup (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version (official documentation).

A dirty sensor, a worn printhead or a damaged platen roller can be spotted before it fails during a preventive maintenance visit.

Explore TIMCOD preventive maintenance

Calibration: my Zebra ZT420 skips labels or prints out of position

The official procedure for manually calibrating the ribbon and media sensors, then the causes Zebra lists when auto calibration fails or the image drifts.

How do I calibrate a Zebra ZT420 that skips labels?

Symptoms: skipped labels, drifting image, ribbon not detected, labels treated as continuous media.

Short answer: With the printer ready, press and hold PAUSE and CANCEL for 2 seconds. Open the printhead, leave only the backing between the sensors, remove the ribbon, close and press PAUSE. Then place a label back under the sensors, reload the ribbon, close and press PAUSE again.

Likely cause

Zebra asks you to calibrate when you change the size or type of ribbon or media, or when the printer skips labels, the image drifts horizontally or vertically, the ribbon is not detected or separate labels are treated as continuous media.

Caution: Zebra warns that the printhead may be hot and can cause severe burns: let it cool before opening the printhead or touching it. The quick reference guide also asks you to remove your jewellery before loading media or ribbon, and to discharge static electricity before touching the printhead.

Official manual calibration procedure

With the printer in the ready state, start calibration: press and hold PAUSE + CANCEL for 2 seconds, or choose START in the TOOLS or SENSORS menu (MEDIA/RIBBON CAL item, RIGHT SELECT button). The STATUS and SUPPLIES lights flash yellow once, then PAUSE flashes yellow.
Open the printhead with its lever.
Pull about 203 mm (8 inches) of media out of the printer and remove the labels from that length so that only the backing is left.
Pull the media back into the printer so that only the backing is between the media sensors (display: LOAD BACKING, REMOVE RIBBON).
Remove the ribbon, if there is one.
Lower the lever until the printhead locks.
Press PAUSE to start media calibration: PAUSE goes off and SUPPLIES flashes (display: CALIBRATING, PLEASE WAIT). At the end, SUPPLIES stops flashing and PAUSE flashes yellow (display: RELOAD ALL).
Open the printhead again and pull the media forward until a label is under the sensors.
Reload the ribbon if there is one, lock the printhead and close the compartment door.
Press PAUSE to enable printing again, then FEED: if a single label advances each time you press it, the printer is calibrated.

Zebra asks you to follow all the steps, even if only one sensor needs adjusting; pressing and holding CANCEL cancels the procedure at any time. The display labels quoted come from the extract of the 2013 ZT400 guide published by Zebra. Auto calibration is set with POWER UP ACTION or HEAD CLOSE ACTION (see the auto calibration entry).

Sources: Performing Manual Sensor Calibration (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Series User Guide P1066582-001, Calibrate the Ribbon and Media Sensors (PDF extract, pp. 119–123) (opens in a new window) – extract from the ZT400 user guide (2013 edition) published by Zebra · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version · ZT400 Series Quick Reference Guide (P1060608-004) (opens in a new window) – Zebra ZT400 Series quick reference guide (official documentation).

Why does auto calibration fail on my Zebra ZT420?

Symptom: “Auto Calibrate failed”, or separate labels treated as continuous media.

Short answer: According to Zebra, the media or ribbon is incorrectly loaded, the sensors do not detect the media or ribbon, the sensors are dirty or incorrectly positioned, or the media type is set incorrectly. Reload, clean and reposition the sensors, check MEDIA TYPE, then do a manual calibration.

Likely cause

The “Printing Issues” and “Miscellaneous Issues” tables list: media or ribbon incorrectly loaded, sensors not detecting the media or ribbon, sensors dirty or incorrectly positioned, media type set incorrectly. If separate labels are treated as continuous media, the printer has not been calibrated for that media, or it is set for continuous media.

What to do

Reload the media and ribbon following the “Loading the Media” and “Loading the Ribbon” procedures.
Clean the sensors and check that they are correctly positioned. According to the guide, brush, blow or vacuum the lint and dust out of the media and ribbon paths, then off the media, ribbon and label taken sensors.
Set MEDIA TYPE (SETTINGS menu) to the actual type: GAP/NOTCH, CONTINUOUS or MARK.
Run a manual calibration (see the calibration entry).
For auto calibration, set POWER UP ACTION (at power-up) or HEAD CLOSE ACTION (when the printhead is closed), TOOLS menu. CALIBRATE adjusts the sensor levels and thresholds, measures the label length and feeds the media to the next gap; SHORT CAL sets the thresholds without adjusting the sensor gain.

The other possible values for POWER UP ACTION and HEAD CLOSE ACTION are FEED, LENGTH and NO MOTION.

Sources: Printing Issues (opens in a new window) – Zebra ZT400 Series user guide · Miscellaneous Issues (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version (official documentation).

Why does the print on my Zebra ZT420 shift from one label to the next?

Symptoms: loss of registration, skipped labels, vertical drift of the top of the label.

Short answer: Zebra mainly cites a calibration that needs redoing, a dirty platen roller, incorrectly positioned media guides or an incorrectly set media type. Clean the platen roller, reposition the guides, check MEDIA TYPE, then calibrate.

Likely cause

The “Printing Issues” table links loss of registration, skipped labels and vertical drift to: printer not calibrated, dirty platen roller, incorrectly positioned media guides, media type set incorrectly (separate labels with a continuous setting), media or ribbon incorrectly loaded, printhead pressure set incorrectly, incorrect label format, or media outside specifications.

What to do

Clean the printhead and the platen roller (see the printhead cleaning entry).
Position the media guides correctly: the guide should just touch the edge of the media.
Set MEDIA TYPE (SETTINGS menu) to GAP/NOTCH, CONTINUOUS or MARK according to the media loaded.
Calibrate the printer (see the calibration entry).
Press FEED. If one label advances each time you press it, the Zebra article advises checking the label format and the driver or software settings, which can override those of the printer.
Check the setting of the printhead pressure dials (see the printhead pressure entry).
Use media that meets the specifications: according to the guide, the gaps or notches between labels must measure 2 to 4 mm and be evenly spaced.

Sources: Printing Issues (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Series Printers: Solving Media Out Errors and Calibrating the Printer – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Performing Manual Sensor Calibration (opens in a new window) · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version (official documentation).

Ribbon problems on the Zebra ZT420: wrinkling, breaking, end of ribbon not detected

Wrinkled or melted ribbon, ribbon that stalls or whose end is not detected: the causes and solutions from the “Ribbon Issues” table and from the Zebra article on ZT400 Series ribbon.

Why is the ribbon on my Zebra ZT420 wrinkling?

Symptoms: wrinkled ribbon, thin diagonal grey lines on the labels, long unprinted areas.

Short answer: According to Zebra, the ribbon is incorrectly loaded, the darkness is too high, the printhead pressure is set incorrectly or the media is moving sideways. Reload the ribbon, lower the darkness, balance the pressure of the two dials and adjust the media guide.

Likely cause

The “Ribbon Issues” table lists: ribbon incorrectly loaded, incorrect burn temperature (darkness), incorrect or uneven printhead pressure, media not feeding straight and moving from side to side, printhead or platen roller incorrectly installed.

What to do

Reload the ribbon correctly (“Loading the Ribbon” procedure).
Set PRINT DARKNESS to the lowest level that suits your application.
Set the printhead pressure to the minimum that gives good quality, balancing it across the width of the media (see the printhead pressure entry).
Adjust the media guide so that it holds the media without any play.
The Zebra article on ZT400 Series ribbon also advises increasing the tension of the ribbon supply spindle and checking that the media and ribbon combination suits the application, as excessive pressure or darkness can wrinkle the ribbon.

When to call a technician: if the media keeps moving sideways, or if the printhead or platen roller is incorrectly installed, Zebra asks you to call a technician.

According to the “Printing Issues” table, wrinkled ribbon leaves thin diagonal grey lines on blank labels and can cause long streaks with no print.

Sources: Ribbon Issues (opens in a new window) – Zebra ZT400 Series user guide · Printing Issues (opens in a new window) – Zebra ZT400 Series user guide · Resolving Ribbon Issues on ZT400 Series Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Ribbon Issues (opens in a new window) (official documentation).

Why does the ribbon on my Zebra ZT420 break, melt or jam?

Symptoms: broken or melted ribbon, ribbon that stalls during printing.

Short answer: According to Zebra, the darkness is too high or the ribbon is coated on the wrong side for this printer. Lower the darkness, clean the printhead and use ribbon coated on the outside, unless the optional spindle for ribbon coated on the inside is installed.

Likely cause

The “Ribbon Issues” table attributes broken or melted ribbon to darkness set too high or to ribbon coated on the wrong side. The Zebra article on ZT400 Series ribbon also covers ribbon that stalls: coated side facing the wrong way, ribbon supply spindle tension, unbalanced printhead pressure, unsuitable darkness or ribbon and media combination.

What to do

Lower the PRINT DARKNESS setting (SETTINGS menu) and clean the printhead thoroughly (see the printhead cleaning entry).
Check the coated side: the printer only uses ribbon coated on the outside, unless the optional spindle for ribbon coated on the inside is installed.
Adhesive test: press the sticky corner of a label onto the outer surface of the ribbon roll, then peel it off. If ink particles remain on the label, the outer side is coated.
Scratch test: unwind a little ribbon, place its outer side on a sheet of paper and scratch the inner side with your fingernail. A mark on the paper indicates that the outer side is coated.
Match the darkness to the ribbon: the Zebra article states that a wax ribbon should not go above a setting of about 23 to 25, while a resin ribbon can take higher values; pair a wax ribbon with paper media and a resin ribbon with synthetic media.
If the ribbon stalls, the article advises setting the ribbon supply spindle tension to low and increasing the printhead pressure so that it is balanced across the width of the media.

For the ZT420, the article refers to a maintenance kit for the ribbon supply spindle (ZT420 Ribbon Supply Spindle Maintenance Kit) when this spindle needs replacing. The guide also recommends a ribbon wider than the media, to protect the printhead from wear.

Sources: Ribbon Issues (opens in a new window) – Zebra ZT400 Series user guide · Resolving Ribbon Issues on ZT400 Series Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Ribbon Issues (opens in a new window) · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version (official documentation).

Why does my Zebra ZT420 produce blank labels when it seems to be printing?

Symptom: the labels come out with no print at all, while the printer seems to be working normally.

Short answer: According to Zebra, the media does not match the print mode: thermal transfer labels only print with a ribbon. Scratch the label with your fingernail; if there is no black mark, load a ribbon and set PRINT METHOD to THERMAL TRANS.

Likely cause

The Zebra article on unprinted labels (ZM and ZT series, including the ZT410 and ZT420 and their RFID versions) gives a single cause: media that is not direct thermal. Direct thermal labels turn black when heated, whereas thermal transfer labels need the ink from a ribbon.

What to do

Do the scratch test: quickly scratch the label surface with your fingernail. A black mark indicates direct thermal media.
No black mark: the media is thermal transfer. Load a ribbon coated on the outside and wider than the media, then set PRINT METHOD to THERMAL TRANS (SETTINGS menu).
Black mark: the media is direct thermal and is used without ribbon; set PRINT METHOD to DIRECT THERMAL.

The article states that it does not apply if the printer prints an image on only part of the labels.

Sources: Unprinted Labels When Attempting to Print Using a ZM or ZT Series Printer – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Ribbon — How can I tell if media is Direct Thermal or Thermal Transfer? (opens in a new window) · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version (official documentation).

Several of these faults involve the ribbon or labels used. TIMCOD, Zebra reseller, supplies labels, thermal transfer ribbons and printheads for thermal printers (pages in French).

Zebra ZT420 print quality: faded print, uneven print, unreadable barcodes

Printhead cleaning, darkness, speed, dial pressure and print width: the settings Zebra recommends checking before replacing parts.

Why does my Zebra ZT420 print too light or too dark?

Symptoms: print too light or too dark over the whole label, marks or smudges.

Short answer: Zebra cites a dirty printhead, incorrectly set darkness or speed, incorrect printhead pressure and an unsuitable label and ribbon combination. Clean the printhead and the platen roller, then set the darkness and speed as precisely as possible.

Likely cause

For poor print quality, the “Printing Issues” table lists: incorrectly set speed or darkness, incompatible label and ribbon combination, dirty printhead, incorrect or uneven printhead pressure. For print that is too light or too dark over the whole label, it adds supplies not designed for high speed and a ribbon used with direct thermal media; for marks or smudges, supplies not designed for high speed.

Caution: Zebra recommends switching the printer off before working near the open printhead (temporary settings, such as label formats, are then erased and will need to be reloaded). Discharge static electricity before touching the printhead, by touching the printer's metal frame or by using an antistatic wrist strap and mat. The printhead may be hot: let it cool to avoid burns.

Official printhead cleaning procedure, then settings

Have ready a swab from the Zebra preventive maintenance kit (part number 47362, or 105950-035 for a multi-pack), or a lint-free cloth or clean swab moistened with 99.7% isopropyl alcohol.
Lift the media compartment door, let the printhead cool, then open it by raising the printhead release lever.
Remove the ribbon (if there is one) and the media.
Wipe the brown strip on the printhead from one end to the other with the swab, then let the solvent evaporate.
Turn the platen roller by hand while cleaning it thoroughly with the swab, then let the solvent evaporate.
Reload the ribbon (if there is one) and the media, lower the lever until the printhead locks, close the door and press PAUSE: depending on the settings, the printer may calibrate or feed a label.
If the quality does not improve, the guide recommends Save-A-Printhead cleaning film, available from an authorised Zebra reseller.
Then set PRINT SPEED (2 to 6 inches per second) to the lowest speed that suits your application, and PRINT DARKNESS (0.0 to 30.0) to the lowest setting that gives good quality; the FEED self test helps you find the right value (see the barcodes entry). Also set the printhead pressure to the minimum needed (see the printhead pressure entry).
Check the label and ribbon combination: use supplies designed for high speed and, if necessary, try another type of media or ribbon. If the label turns black when you scratch it with a fingernail, it is direct thermal and is used without ribbon.
For faded print, the Zebra article on ZT410 and ZT420 print quality also advises increasing the darkness or the printhead pressure, reducing the speed and checking that the ribbon is not slipping.

According to the Zebra schedule, clean the printhead, the platen roller and the media and ribbon paths after every roll of media in direct thermal mode (or every 500 feet of fanfold media), and after every roll of ribbon in thermal transfer mode; the sensors are cleaned by blowing air on them, and the tear-off or peel-off bar once a month. The printhead and platen roller are replaceable wear parts whose service life can be extended by regular cleaning.

Sources: Printing Issues (opens in a new window) – Zebra ZT400 Series user guide · Resolving Print Quality Issues on ZT410 and ZT420 Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Printing Issues (opens in a new window) · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version · ZT400 Series Quick Reference Guide (P1060608-004) (opens in a new window) – Zebra ZT400 Series quick reference guide · Replacing Printer Components (opens in a new window) – Zebra ZT400 Series user guide (official documentation).

Why does my Zebra ZT420 print lighter on one side of the label?

Symptoms: one side of the label fainter, thick media, media drifting sideways.

Short answer: The pressure of the two printhead dials is unevenly distributed. If the left side is faded, turn the inner dial up by one position; if it is the right side, the outer dial. Zebra advises the lowest pressure that gives good quality.

Likely cause

The “Printing Issues” table attributes print that is too light or too dark on one side only to incorrect or uneven printhead pressure. According to the guide, the pressure should also be adjusted for thick media or media that drifts from side to side.

What to do

Set the two pressure dials (inner and outer, graduated from 1 to 4) to the starting values in the Zebra table for the ZT420: 51 mm (2-inch) media: inner dial 4, outer 1; 76 mm (3-inch): 3.5 and 1; 102 mm (4-inch): 3 and 2; 127 mm (5-inch) and wider: 2.5 and 2.5.
Print and check the result.
Insufficient pressure across the whole width: turn both dials up by one position.
Left side too light: turn the inner dial up by one position. Right side too light: turn the outer dial up by one position.
Media drifting to the left: turn the outer dial up or the inner dial down by one position. Media drifting to the right: turn the inner dial up or the outer dial down by one position.

The starting table on the Zebra page differs between the ZT410 and ZT420: use the row for your model.

Sources: Adjusting the Printhead Pressure (opens in a new window) – Zebra ZT400 Series user guide · Printing Issues (opens in a new window) – Zebra ZT400 Series user guide · Resolving Print Quality Issues on ZT410 and ZT420 Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Printing Issues (opens in a new window) (official documentation).

Why won't the barcodes printed by my Zebra ZT420 scan?

Symptoms: barcode unreadable by the scanner, bars too thick or incomplete.

Short answer: According to Zebra, the barcode is out of specification because the print is too light or too dark, or the blank area around the code is too small. Adjust the darkness or speed using the FEED self test, and leave at least 3.2 mm of blank space around the code.

Likely cause

The “Printing Issues” table cites print that is too light or too dark, putting the barcode out of specification, and insufficient blank space around the code.

What to do (including the FEED self test)

Leave at least 3.2 mm (1/8 inch) between the barcode and other printed areas, and between the barcode and the edge of the label.
Print a configuration label to note the current settings (FEED + CANCEL for 2 seconds, printer ready).
Switch the printer off, then hold down FEED while switching it back on, until the first light on the panel goes off: this is the FEED self test.
The printer prints labels at 2 and 6 inches per second, with a relative darkness ranging from -3 to +3 compared with the current setting; each label shows its relative value and its speed.
Choose the best-printed label: with a barcode verifier if possible, otherwise by eye or with your scanner. According to Zebra, print that is too dark widens the bars and fills in small characters; print that is too light leaves incomplete bars and spaces.
Add the relative darkness value of that label to the darkness noted on the configuration label, then set PRINT DARKNESS and, if necessary, PRINT SPEED accordingly.

The Zebra article on ZT410 and ZT420 print quality also recommends a quiet zone equal to 10 times the width of the narrowest bar, and a PAUSE self test to spot missing printhead elements. Use full-width media for the self tests: otherwise, the printer may print on the platen roller.

Sources: Printing Issues (opens in a new window) – Zebra ZT400 Series user guide · 7. ZT410_ZT420 User Guide - Feed Self-Test (P1066582-001, pp. 162–164) (opens in a new window) – attachment to the Zebra article “Resolving Print Quality Issues on ZT410 and ZT420 Printers” · Resolving Print Quality Issues on ZT410 and ZT420 Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Printing Issues (opens in a new window) · Printer Diagnostics (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version (official documentation).

Why is the print on my Zebra ZT420 cut off on the right-hand side?

Symptoms: image truncated on the right, part of the format not printed.

Short answer: According to the Zebra article on ZT410 and ZT420 print quality, check the print width (PRINT WIDTH) on the display and in the driver or software, use a ribbon wider than the labels and remove any debris or label stuck under the printhead.

Likely cause

The Zebra article gives three causes for an image cut off on the right: incorrectly set print width, ribbon narrower than the labels, debris or a label stuck on the printhead. The guide states that a width set too narrow prevents part of the format from printing.

Caution: Zebra warns that the printhead may be hot and can cause severe burns: let it cool before opening the printhead or touching it.

What to do

Check PRINT WIDTH in the SETTINGS menu, then the width setting in the driver or label software. According to the guide, PRINT WIDTH accepts up to 1,344 dots at 203 dpi and 1,984 at 300 dpi on the ZT420.
Use a ribbon wider than the labels.
Remove any debris or labels stuck on the printhead.

Conversely, a width set too wide wastes formatting memory and can cause printing on the platen roller.

Sources: Resolving Print Quality Issues on ZT410 and ZT420 Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Printing Issues (opens in a new window) · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version (official documentation).

Cleaning the printhead, platen roller and sensors is part of TIMCOD preventive maintenance visits. Between visits, TIMCOD also supplies printer cleaning kits.

Schedule preventive maintenance

Zebra ZT420 printhead: non-genuine printhead, thermistor, white lines

These cases concern the printhead itself. According to the Zebra guide, several of them are a job for a technician.

Why are the STATUS, PAUSE and DATA lights on my Zebra ZT420 red after a printhead change?

Non-genuine printhead alert · Lights: STATUS, PAUSE and DATA solid red.

Short answer: According to the ZT400 Series error message table, the installed printhead is not a genuine Zebra printhead. The intended solution is to install a genuine Zebra printhead.

Likely cause

The “Error Message Lookup” table and the quick reference guide attribute this combination of lights to a printhead that is not a genuine Zebra part. The quick reference guide adds a related case: STATUS flashing red when the printer cannot read the printhead resolution (dpi).

Caution: The Zebra quick reference guide asks you to discharge any built-up static electricity before touching the printhead.

What to do

Install a genuine Zebra printhead.
To obtain the part or have the printhead replaced, contact your site's support, the Zebra partner who sold you the printer or Zebra support, with the serial number, model and firmware version.

If only the STATUS light flashes red, the printer cannot read the printhead resolution setting: the quick reference guide gives no solution; contact Zebra support or your partner.

Sources: Error Message Lookup (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Series Quick Reference Guide (P1060608-004) (opens in a new window) – Zebra ZT400 Series quick reference guide · Servicing the Printer (opens in a new window) – Zebra ZT400 Series user guide (official documentation).

Why does the display on my Zebra ZT420 alternate between several printhead messages?

One or more printhead messages, displayed alternately · Light: STATUS solid yellow.

Short answer: According to Zebra, the printhead data or power cable is not properly connected, or the printhead thermistor is faulty. Both cases call for a technician: reconnecting the cable or replacing the printhead.

Likely cause

The “Error Message Lookup” table states that the printer shows one of these messages or alternates between them when the printhead data or power cable is not properly connected, or when the thermistor is faulty.

What to do

Contact a technician: for this case, the Zebra guide does not provide for any action by the user.
Before calling support, note the serial number, model and firmware version, as Zebra asks.

When to call a technician: printhead cable not properly connected or faulty thermistor: Zebra leaves reconnecting the cable or replacing the printhead to a technician.

Sources: Error Message Lookup (opens in a new window) · Servicing the Printer (opens in a new window) – Zebra ZT400 Series user guide (official documentation).

Why does my Zebra ZT420 print vertical white lines?

Symptoms: white lines in the print, long streaks with no print across several labels.

Short answer: Clean the printhead first: residue on the heating elements leaves white lines. If long streaks with no print persist, a printhead element is damaged and Zebra asks you to call a technician. Wrinkled ribbon can also be the cause.

Likely cause

The “Printing Issues” table cites a damaged print element or wrinkled ribbon for long streaks with no print. The Zebra article on ZT410 and ZT420 print quality links white lines to dirty printhead elements, or to a faulty element if the defect persists.

Caution: Zebra warns that the printhead may be hot and can cause severe burns: let it cool before opening the printhead or touching it.

What to do

Clean the printhead elements (see the printhead cleaning entry).
If the residue does not come off with the swab, the Zebra article mentions more thorough cleaning with a cleaning film.
Run a PAUSE self test to check whether any printhead elements have stopped working: with the printer off, hold down PAUSE while switching it on until the first light on the panel goes off. It prints 15 labels at the slowest speed, then pauses; compare them with the example in the guide. Hold down CANCEL to exit the test.
If the streaks come with ribbon wrinkling, see the wrinkled ribbon entry.

When to call a technician: if the lines persist after cleaning, a print element on the printhead is damaged: Zebra asks you to call a technician.

TIMCOD supplies printheads for thermal printers (page in French).

Zebra ZT420 connectivity: nothing prints, network, Wi-Fi, USB flash drive

DATA light, serial link, IP address, Wi-Fi and USB host port: the communication causes documented by Zebra for the ZT400 Series.

Why does my Zebra ZT420 print nothing when I send a label?

Symptoms: label format not recognised, DATA light not flashing, or flashing with no print.

Short answer: If the DATA light does not flash, the communication parameters are incorrect. If it flashes but nothing prints, the prefix and delimiter characters do not match the format, or the data sent is incorrect.

Likely cause

The “Communication Problems” table distinguishes two cases: DATA not flashing (incorrect communication parameters); DATA flashing with no print (the printer's prefix and delimiter differ from those of the format, or incorrect data). On a serial link, incorrect parameters also cause the image to skip, shift or distort after a few labels.

What to do

DATA not flashing: check the communication parameters in the driver or software.
On a serial link, check the port parameters (Port Settings), use a null modem cable or adapter, and check that the handshake protocol matches that of the computer; also check that flow control is identical on both sides and that the cable length is within specifications.
With a printer driver, check its communication parameters for your connection, then reinstall it.
DATA flashing with no print: check Control Character and Delimiter Character (Language Settings), which must match the label format.
Check that the computer's communication parameters match those of the printer, then check the label format.
To see what the printer is receiving, enable communication diagnostics mode (PAUSE + FEED for 2 seconds, printer ready, or COMMUNICATION DIAGNOSTICS MODE in the TOOLS menu): the printer prints all the data received in hexadecimal.

Sources: Communication Problems (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version (official documentation).

Why does my Zebra ZT420 change its IP address or fail to connect to the network?

Symptoms: new IP address after switching off, wired or Wi-Fi connection impossible after manual entry, NETWORK light red.

Short answer: According to Zebra, the IP address changes because the network settings cause it to be reassigned: fix it by setting the IP protocol to PERMANENT. After any manual entry of the address, subnet mask or gateway, reset the network (Reset Network) so that the values take effect.

Likely cause

The “Miscellaneous Issues” table lists: network settings that reassign the address, network not reset after a change, ESSID not entered on Wi-Fi, ESSID or another value entered incorrectly. According to the quick reference guide, the NETWORK light solid red indicates an Ethernet or Wi-Fi error: the printer is not connected to the network.

What to do

Fixed address on Ethernet: from the Home menu (LEFT SELECT button), open the network menu, set WIRED IP PROTOCOL to PERMANENT, enter WIRED IP ADDRESS, WIRED SUBNET MASK and WIRED GATEWAY, then run RESET NETWORK. The Zebra article states that an active network link is required and that the NETWORK light should then turn solid green.
The guide gives the same method for the wireless print server: note the IP address, subnet mask and gateway, set the corresponding IP protocol to PERMANENT, enter the values, then reset the network (Menu > Connections > Networks > Reset Network) and confirm with OK.
Wi-Fi: enter the ESSID of your access point. Zebra gives the Set/Get/Do command ! U1 setvar "wlan.essid" "value"; the ESSID is on the router label, or available from your network administrator if it has been changed. If the printer still does not connect, reset the network, then switch the printer off and on again.
Print a network configuration label (FEED + CANCEL for 2 seconds, printer ready), check the values, correct any errors, then reset the network.

NETWORK light according to the quick reference guide. On Ethernet: off, no link; solid green, 100 Base link; solid yellow, 10 Base link; solid red, Ethernet error. On Wi-Fi: flashing red, association in progress; flashing yellow, authentication in progress; solid green, connected with a strong signal; flashing green, connected with a weak signal; solid red, WLAN error. To reset only the network settings to factory defaults, see the reset entry.

Sources: Miscellaneous Issues (opens in a new window) – Zebra ZT400 Series user guide · Changing the Wired TCP/IP Settings Through the ZT410 or ZT420 LCD Menu of the Printer – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Network Settings (opens in a new window) · ZT400 Series Quick Reference Guide (P1060608-004) (opens in a new window) – Zebra ZT400 Series quick reference guide · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version (official documentation).

Why doesn't my Zebra ZT420 recognise my USB flash drive?

Symptoms: USB flash drive or device not recognised on the host port, files not read, message about a disabled USB host port.

Short answer: According to Zebra, the printer only accepts USB flash drives of up to 1 TB, and some devices need their own power supply. If a message says that the USB host port is disabled, select YES to use the device.

Likely cause

The “Miscellaneous Issues” table cites a flash drive larger than 1 TB and a device without an external power supply. The error message table adds the case of a USB device connected to a disabled host port.

What to do

Use a USB stick of 1 TB or less.
If the device needs an external power supply, connect it to a working power supply.
If the display reports a disabled USB host port, select YES to use the device (the guide also gives an SGD command for this).

Sources: Miscellaneous Issues (opens in a new window) · Error Message Lookup (opens in a new window) – Zebra ZT400 Series user guide (official documentation).

Zebra ZT420 cutter: what to do about a cutting error?

The cutter alert, its lights and Zebra's instructions before inspecting and cleaning the cutter module.

Why does my Zebra ZT420 report a cutter error?

Alert: Cut Error · Lights: STATUS solid red, PAUSE solid yellow.

Short answer: According to Zebra, the cutter blade is in the media path; the help page for the alert cites a dirty cutter or a faulty cutter sensor. Switch off and unplug the printer, inspect the cutter module for debris and clean it if necessary.

Likely cause

The “Error Message Lookup” table states that the cutter blade is in the media path. The Zebra help page for the ZT400 Series “CutError” alert cites a dirty cutter or a faulty cutter sensor.

Caution: The cutter blade is sharp: Zebra asks you not to touch it or rub it with your fingers. Switch off and unplug the printer before working on it.

What to do (official cutter cleaning procedure)

Switch the printer off and unplug the power cord.
Lift the media compartment door and remove the loaded media.
Remove the thumbscrew and lock washer from the cutter cover, then the cover. If necessary, turn the cutter motor thumbscrew to expose the V-shaped blade fully.
Wipe the upper cutting surface and the blade with a swab from the preventive maintenance kit or a swab moistened with isopropyl alcohol, then let it evaporate.
Moisten a clean swab with a general-purpose, high-viscosity silicone or PTFE oil, then apply a thin, even coat to all exposed surfaces of both blades. Remove any excess so that it does not reach the printhead or the platen roller.
Refit the cover with its screw and washer, close the door, plug the printer back in and switch it on: the blade returns to its operating position.

When to call a technician: if the cutter still does not work properly after cleaning and lubrication, Zebra asks you to contact an authorised service technician.

According to the Zebra cleaning schedule, the cutter is cleaned after every roll of continuous adhesive media (or more often depending on use), and after two or three rolls of card or label backing. The cutter module is the only part to be lubricated: do not lubricate any other parts, as some commercially available lubricants damage the finish and the mechanical parts. The same combination of lights (STATUS red, PAUSE yellow) also indicates an open printhead: see the Head Open entry.

Zebra ZT420 settings: factory defaults, settings not applied

How to reload the factory defaults, the network configuration or the last saved configuration, and why a setting may not be applied.

How do I reset a Zebra ZT420 to factory defaults?

Need: return to the factory settings, the last saved configuration or the original network settings.

Short answer: In the TOOLS menu, LOAD DEFAULTS offers FACTORY (factory settings except network), NETWORK (print server reset) and LAST SAVED (last saved configuration). At power-up, FEED + PAUSE loads the factory defaults and CANCEL + PAUSE the network defaults.

Likely cause

Zebra warns that you will need to re-enter all manually changed settings after loading the defaults.

Official procedure

From the menu: TOOLS > LOAD DEFAULTS, then FACTORY, NETWORK or LAST SAVED.
With the buttons: with the printer off, hold down FEED + PAUSE (factory defaults) or CANCEL + PAUSE (network) while switching the printer on, until the first light on the panel goes off. No label is printed.
From the printer's web page: View and Modify Printer Settings > Restore Default Configuration (factory), Print Server Settings > Reset Print Server (network), View and Modify Printer Settings > Restore Saved Configuration (last configuration).
After returning to factory defaults, calibrate the sensors (see the calibration entry).

In ZPL, the corresponding commands are ^JUF (factory), ^JUN (network) and ^JUR (last configuration). On a wireless print server, the NETWORK option also re-associates the printer with the Wi-Fi network.

Sources: ZT400 Series Industrial Printer User Guide (PDF) › Loading Defaults or Last-Saved Values (opens in a new window) – extract from the ZT400 user guide (2013 edition) published by Zebra · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version (official documentation).

Why are the settings on my Zebra ZT420 not being applied?

Symptoms: change has no effect, setting changes by itself, setting cannot be changed, setting reverts to its previous value.

Short answer: According to Zebra, some parameters are set incorrectly, or a label format, a command or the software sending the formats changes or blocks the setting. Check the parameters, switch the printer off and on again and check your formats.

Likely cause

The “Miscellaneous Issues” table lists: parameters set incorrectly; a firmware setting or command preventing the change; a command in a label format resetting the parameter to its previous value. If the problem persists, the main logic board may be faulty.

What to do

Check the parameters, change them or reset them, then switch the printer off (O) and back on (I).
If a parameter cannot be changed, check your label formats and the settings of the software sending the formats. The Zebra ZPL programming guide (zebra.com/manuals) details the commands; otherwise, the guide refers you to a technician.
If a parameter reverts to its previous value, look for the command in the format that changes it.
The Zebra article on print quality points out that the driver or application can override the pressure, darkness and speed set on the printer: test with a PAUSE self test to rule out the computer.

When to call a technician: if a parameter keeps reverting to its previous value, the main logic board may be faulty: Zebra asks you to call a technician.

Sources: Miscellaneous Issues (opens in a new window) – Zebra ZT400 Series user guide · Resolving Print Quality Issues on ZT410 and ZT420 Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) · ZT400 Series Industrial Printer User Guide › Printing Issues (opens in a new window) (official documentation).

Zebra ZT420 RFID: voided labels, stopping at the inlay, RFID settings missing

These entries apply only to the RFID version of the ZT420. They are based on the “RFID Issues” table in the ZT400 Series guide.

Why does my Zebra ZT420 RFID void all labels or too many labels?

Symptoms: RFID enabled, every label is voided (VOID), or too many labels voided per roll.

Short answer: According to Zebra, the printer is not calibrated for the media, the label is not Gen 2, the RFID reader is not communicating, a radio source is interfering with encoding or the programming position is incorrect. Calibrate manually, check the label type and move the printer away from other RF sources.

Likely cause

For all labels being voided, the “RFID Issues” table lists: printer not calibrated for the media, unsupported label (only Gen 2 labels are supported), RFID reader unreachable, RF interference, incorrect label software settings, incorrect programming position, incorrect RFID ZPL or SGD commands. For low yield: labels outside RFID specifications, unsuitable read and write power, RF interference, outdated printer or reader firmware.

What to do

Calibrate the printer manually (see the calibration entry).
Check that the labels are Gen 2 and that the transponder placement meets Zebra specifications (zebra.com/transponders).
Switch the printer off (O), wait 10 seconds, then switch it back on (I) to restore communication with the RFID reader.
Move the printer away from fixed RFID readers and other RF sources, and keep the compartment door closed during RFID programming.
Check that the label software settings match those of the printer: they override them.
Check the RFID programming position (in the printer or the software) and return to the default value if necessary; check your RFID ZPL or SGD commands against the RFID Programming Guide 3.
If too many labels are voided, adjust the RFID read and write power and update the printer and reader firmware (zebra.com/firmware).

When to call a technician: if the printer still does not communicate with the RFID reader after restarting, the reader may be faulty or incorrectly connected: contact technical support or a Zebra-authorised RFID technician.

In the RFID menu, RFID TAG CALIBRATION starts RFID label calibration, which is separate from media and ribbon calibration. PROGRAMMING POSITION, RFID READ POWER and RFID WRITE POWER (0 to 30) should only be set manually if this calibration does not give the desired result. These cases only concern the RFID version of the ZT420; the RFID table is shared by the ZT400 Series.

Why does my Zebra ZT420 RFID stop at the inlay instead of the gap between labels?

Symptom: the printer stops at the RFID inlay.

Short answer: According to Zebra, the printer measured the label length up to the RFID inlay instead of the gap between labels. Set POWER UP ACTION and HEAD CLOSE ACTION to FEED, then calibrate manually.

Likely cause

The “RFID Issues” table states that calibration took the RFID inlay for the end of the label, instead of the gap between two labels.

What to do

Set POWER UP ACTION and HEAD CLOSE ACTION to FEED (TOOLS menu), as appropriate.
Calibrate the printer manually (see the calibration entry).

Why don't the RFID settings appear on my Zebra ZT420 RFID?

Symptoms: RFID parameters missing from the menu and the configuration label, RFID reader unreachable, DATA light flashing endlessly after a firmware update.

Short answer: According to Zebra, the printer was switched off and back on too quickly for the RFID reader to initialise. Switch it off, wait 10 seconds, switch it back on, then check the RFID settings or a new configuration label.

Likely cause

The “RFID Issues” table lists: restart too quick for the RFID reader to initialise; communication with the RFID subsystem impossible; wrong firmware version loaded (incorrectly programmed labels not voided); failed printer or reader firmware download (DATA light flashing indefinitely).

What to do

Switch the printer off (O), wait 10 seconds, then switch it back on (I).
Check the RFID settings in the menu or on a new configuration label.
If incorrectly programmed labels are not voided, check the firmware version (RFID Programming Guide 3) and load the correct firmware if necessary.
If the DATA light flashes endlessly after a firmware download, switch the printer off, wait 10 seconds, switch it back on and start the download again. Zebra advises switching the printer off and on again before any firmware download.

When to call a technician: if the RFID reader remains unreachable, if the wrong firmware persists or if the update fails again, contact Zebra technical support or an authorised technician: the RFID reader may be faulty or incorrectly connected.

If the “RfidCountryCodeNotSelected” alert appears, no RFID country code is selected: according to Zebra, select your country code to access the RFID functions (on some printers, you are asked at first power-up). These cases appear in the RFID table of the ZT400 Series guide; they concern the RFID version of the ZT420.

Sources: RFID Issues (opens in a new window) – Zebra ZT400 Series user guide · ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version · ZT400 Alert: RfidCountryCodeNotSelected (opens in a new window) – Zebra help pages for ZT400 Series alerts (official documentation).

When should you call a technician for a Zebra ZT420?

The entries above first suggest reloading, adjusting, cleaning or calibrating. In the following cases, the Zebra documentation refers you to a technician:

“Head Open” persisting with the printhead latched: head-open sensor needs replacing.
“Print Head Under Temperature” in a room at a normal temperature: printhead data cable needs reconnecting or printhead needs replacing (thermistor).
Persistent insufficient memory: technician call-out after simplifying the format and settings.
Ribbon wrinkling despite adjustments: media still moving sideways, printhead or platen roller incorrectly installed.
Alternating printhead messages: reconnecting the printhead cable, or replacing the printhead if the thermistor is faulty.
White lines after cleaning: damaged printhead print element.
Cutter still cutting badly after cleaning and lubrication: work by an authorised service technician.
Setting that reverts to its previous value: main logic board possibly faulty.
RFID reader unreachable after restarting: faulty or incorrectly connected RFID reader: technical support or a Zebra-authorised RFID technician.
RFID settings missing or firmware update failing repeatedly: Zebra technical support or an authorised technician.
Printer frozen, stuck at start-up or incomplete display: electronics or firmware fault, main logic board or display needs replacing.

Is your Zebra ZT420 in one of these situations? TIMCOD corrective maintenance includes phone support (hotline), repair to working order, express exchange and, as an option, SWAP. The repair request form is in French.

Request a repair Contact TIMCOD

Avoiding recurring faults on the Zebra ZT420: preventive maintenance

Several entries in this guide point to sensors that are badly positioned or dirty, a printhead or platen roller that needs cleaning, or unsuitable settings or consumables. These are exactly the points a preventive maintenance visit checks before they cause a breakdown.

TIMCOD preventive maintenance is part of the through-life maintenance (MCO) TIMCOD provides for your fleet (page in French): scheduled preventive visits by certified technicians, with a detailed report. What it brings to a ZT420 fleet:

Fewer breakdowns, less downtimeFewer production interruptions caused by label printers.
Worn parts detected in timePrinthead, platen roller, sensors: spotted before they cause a breakdown.
Regular cleaning and checksPrinthead, rollers and sensors cleaned and checked at every visit.
Longer service lifeA well-maintained, properly adjusted printer lasts longer.
Print quality maintainedLegible barcodes, with darkness and printhead pressure suited to your consumables.
Fewer emergency call-outsIncidents are handled during scheduled visits rather than as emergency repairs.
Controlled maintenance costsA predictable budget instead of unplanned repairs.
Specialist Zebra techniciansSupport from teams who know your equipment.

In addition, TIMCOD corrective maintenance includes phone support (hotline), repair to working order, express exchange and, as an option, SWAP. Maintenance contracts come in three levels (Essentiel, Confort, Premium).

Zebra ZT420 troubleshooting: frequently asked questions

How do I calibrate a Zebra ZT420?

With the printer ready, press and hold PAUSE and CANCEL for 2 seconds. Open the printhead, leave only the backing between the sensors, remove the ribbon, close and press PAUSE. Then place a label back under the sensors, reload the ribbon, close and press PAUSE again, then FEED to check that only one label advances. See the detailed entry.

Why does my Zebra ZT420 show “Media Out” with labels loaded?

According to Zebra, the media is incorrectly loaded, the media sensor is incorrectly positioned or the printer is set for separate labels while continuous media is loaded. Reload the roll, check MEDIA TYPE and calibrate. If the problem persists, clean the media sensor and repeat the calibration. See the detailed entry.

What should I do if my Zebra ZT420 shows “Ribbon Out” when the ribbon is in place?

Reload the ribbon, pushing it fully onto the supply spindle, then calibrate the sensors. If the problem continues, print a sensor profile: a ribbon out threshold that is too high is corrected by a new calibration or by LOAD DEFAULTS. With direct thermal labels, set PRINT METHOD to DIRECT THERMAL. See the detailed entry.

How do I clean the printhead on a Zebra ZT420?

Zebra recommends a swab from the preventive maintenance kit, or a clean swab moistened with 99.7% isopropyl alcohol. Switch the printer off, let the printhead cool, open it and remove the ribbon and media, then wipe the brown strip on the printhead from one end to the other and clean the platen roller while turning it. Do this after every roll of media in direct thermal mode, or after every roll of ribbon in thermal transfer mode. See the detailed entry.

Why does my Zebra ZT420 print lighter on one side?

The pressure of the two printhead dials is unevenly distributed. If the left side is faded, turn the inner dial up by one position; if it is the right side, the outer dial. Zebra advises the lowest pressure that gives good quality. See the detailed entry.

How do I reset a Zebra ZT420 to factory settings?

In the TOOLS menu, LOAD DEFAULTS offers FACTORY (factory settings except network), NETWORK (print server) and LAST SAVED (last saved configuration). With the printer off, you can also hold down FEED + PAUSE while switching it on for the factory defaults, or CANCEL + PAUSE for the network. Then calibrate the sensors. See the detailed entry.

What do a red STATUS light and a yellow PAUSE light mean on a Zebra ZT420?

This combination indicates either an open printhead or a cutter error. First close the printhead until it locks. If the printer has a cutter, switch it off, unplug it and inspect the cutter module. See the detailed entry.

How do I set a Zebra ZT420 back to French?

Open the LANGUAGE menu from the main menu, scroll through the languages with the UP or DOWN arrow and select your language with OK. The setting can also be reached from the printer's web page, under General Setup. See the detailed entry.

Sources consulted

All the causes, procedures and alerts in this guide come from the pages of the official Zebra documentation listed below (ZT400 Series user guide, PDF extracts of the guide, knowledge base and alert help pages), consulted on 20 October 2026. The user guide is shared by the ZT410 and ZT420.

ZT400 Series Industrial Printer User Guide (opens in a new window) – ZT400 Series Industrial Printer User Guide (docs.zebra.com, home page and table of contents) official
Control Panel (opens in a new window) – ZT400 Series Industrial Printer User Guide (shared by the ZT410 / ZT420) official
Error Message Lookup (opens in a new window) – ZT400 Series Industrial Printer User Guide (shared by the ZT410 / ZT420) official
Printing Issues (opens in a new window) – ZT400 Series Industrial Printer User Guide (shared by the ZT410 / ZT420) official
Ribbon Issues (opens in a new window) – ZT400 Series Industrial Printer User Guide (shared by the ZT410 / ZT420) official
Communication Problems (opens in a new window) – ZT400 Series Industrial Printer User Guide (shared by the ZT410 / ZT420) official
Miscellaneous Issues (opens in a new window) – ZT400 Series Industrial Printer User Guide (shared by the ZT410 / ZT420) official
RFID Issues (opens in a new window) – ZT400 Series Industrial Printer User Guide (shared by the ZT410 / ZT420) official
Printer Diagnostics (opens in a new window) – ZT400 Series Industrial Printer User Guide (shared by the ZT410 / ZT420) official
PAUSE Self Test (opens in a new window) – ZT400 Series Industrial Printer User Guide (shared by the ZT410 / ZT420) official
Performing Manual Sensor Calibration (opens in a new window) – ZT400 Series Industrial Printer User Guide (shared by the ZT410 / ZT420) official
Adjusting the Printhead Pressure (opens in a new window) – ZT400 Series Industrial Printer User Guide (shared by the ZT410 / ZT420) official
Replacing Printer Components (opens in a new window) – ZT400 Series Industrial Printer User Guide (shared by the ZT410 / ZT420) official
ZT400 Series Industrial Printer User Guide (PDF, P1066582-07EN Rev A) (opens in a new window) – ZT400 Series Industrial Printer User Guide, PDF version official
ZT400 Series Quick Reference Guide (P1060608-004) (opens in a new window) – Zebra ZT400 Series quick reference guide official
ZT400 Series User Guide P1066582-001, Calibrate the Ribbon and Media Sensors (PDF extract, pp. 119–123) (opens in a new window) – extract from the ZT400 user guide (2013 edition) published by Zebra official
ZT400 Series Industrial Printer User Guide (PDF) › Loading Defaults or Last-Saved Values (opens in a new window) – extract from the ZT400 user guide (2013 edition) published by Zebra official
7. ZT410_ZT420 User Guide - Feed Self-Test (P1066582-001, pp. 162–164) (opens in a new window) – attachment to the Zebra article “Resolving Print Quality Issues on ZT410 and ZT420 Printers” official
ZT400 Series Printers: Solving Media Out Errors and Calibrating the Printer – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) official
ZT400 Series Industrial Printer User Guide › Performing Manual Sensor Calibration (opens in a new window) official
Video: Fix Media Out Error Code on ZT410 and ZT420 Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) official
ZT400 Series Industrial Printer User Guide › Error Message Lookup — MEDIA OUT (opens in a new window) official
Troubleshooting Ribbon Out Error on ZT410 and ZT420 Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) official
ZT400 Series Industrial Printer User Guide › Error Message Lookup — RIBBON OUT (opens in a new window) official
Resolving Ribbon Issues on ZT400 Series Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) official
ZT400 Series Industrial Printer User Guide › Ribbon Issues (opens in a new window) official
Resolving Print Quality Issues on ZT410 and ZT420 Printers – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) official
ZT400 Series Industrial Printer User Guide › Printing Issues (opens in a new window) official
Unprinted Labels When Attempting to Print Using a ZM or ZT Series Printer – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) official
ZT400 Series Industrial Printer User Guide › Ribbon — How can I tell if media is Direct Thermal or Thermal Transfer? (opens in a new window) official
Changing the Wired TCP/IP Settings Through the ZT410 or ZT420 LCD Menu of the Printer – Zebra knowledge base (link removed on 21 October 2026: the page is no longer available at its former address) official
ZT400 Series Industrial Printer User Guide › Network Settings (opens in a new window) official
ZT400 Alert: Head Open (opens in a new window) – Zebra help pages for ZT400 Series alerts official
ZT400 Alert: Media Out (opens in a new window) – Zebra help pages for ZT400 Series alerts official
ZT400 Alert: CutError (opens in a new window) – Zebra help pages for ZT400 Series alerts official
ZT400 Alert: Print Head Over Temperature (opens in a new window) – Zebra help pages for ZT400 Series alerts official
ZT400 Alert: Print Head Under Temperature (opens in a new window) – Zebra help pages for ZT400 Series alerts official
ZT400 Alert: Ribbon Not Expected (opens in a new window) – Zebra help pages for ZT400 Series alerts official
ZT400 Alert: MediaLow (opens in a new window) – Zebra help pages for ZT400 Series alerts official
ZT400 Alert: RfidCountryCodeNotSelected (opens in a new window) – Zebra help pages for ZT400 Series alerts official
Servicing the Printer (opens in a new window) – ZT400 Series Industrial Printer User Guide (shared by the ZT410 / ZT420) official

On docs.zebra.com, the “Cleaning the Printhead and Platen Roller”, “Cleaning Schedule and Procedures”, “Routine Maintenance”, “Indicator Lights”, “Error Messages”, “Alerts and Error States”, “QuickHelp Pages” and “Performing Auto Calibration” pages of the ZT400 guide (as well as French and Spanish versions, including “Voyants lumineux” and “Nettoyage et lubrification du module de massicot”), “Calibration, Diagnostic, and Other Tools” and “Cleaning the Media Compartment and Sensors” were not consulted for this guide. The PDF extract “ZT400_Clean_Cutter”, the “Printhead Maintenance Guide” in the Zebra knowledge base, the “ZT400 Alert: Ribbon Out” and “RfidNotPresent” help pages and the ZT410 and ZT420 data sheets were not consulted either. The pages of the English PDF P1066582-07EN beyond page 154 (including the “Indicator Lights”, “Error Messages” and “Troubleshooting” sections of the PDF, from page 160 onwards) and the French PDF P1066582-07FR, apart from its identification and table of contents, were not consulted either. These pages and documents are not cited. If the fault falls under these documents, refer to the manufacturer's documentation or ask the TIMCOD technicians.

Does your Zebra ZT420 keep running into problems?

Contact TIMCOD to set up preventive maintenance for your printer fleet: scheduled visits by certified technicians to check, clean and adjust your printers and spot worn parts before they fail.

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