Many of our customers use a Zebra printer to print thermal labels and the Zebra GK420d is still widespread.

In this article, we have collected links to the official user guide, how-to videos by Zebra, and included some key excerpts from the user guide to help you during troubleshooting.

Jump to:

• Link to all Zebra's GK420d How-to videos 
• Download Zebra's GK420d user guide 
• Overview of status lights
• Printing a configuration label
• Overview of Power on/off modes and flash sequences

Overview of Status lights

The status light is placed on top of the printer next to the feed button. It usually lights green constantly, but it may flash or light red or amber to indicate different printer statuses. 

The following table is an excerpt from the official user guide. It is meant as a quick reference during troubleshooting. Please read the manual for a more in-depth explanation.

Status light error resolutions

The following numbers correspond to the numbers in the table above:

1. The printer is not receiving power.
   • Have you turned on the printer power?
   • Check power connections from the wall outlet to the power supply, and from the power supply to the printer.
   • Disconnect the printer from the wall outlet for 30 seconds and then reconnect the printer to the wall outlet.
2. The printer is on and in an idle state.
   • No action necessary.
3. The printer has failed its power on self-test (POST).
   • If this error occurs right after you turn on the printer, contact an authorized reseller for assistance. When the printer is operating normally, the printer status light will be amber for about 10 seconds before turning green (solid or blinking).
   • There is a memory error. If this error occurs after you have been printing, turn the printer power off and on, and then resume printing.
   • The printhead needs to cool down. If this error continues, turn the printer power off for five minutes or more, and then turn on. If the amber light persists, then the printer requires service.
4. The printer is receiving data.
   • As soon as all of the data has been received, the status LED will turn green and the printer will automatically resume operation.
5. The media is out.
   • Follow the instructions for Loading Roll Media on page 11 in the Getting Started section, and then press the Feed button to resume printing.
   • The printhead is open. Close the top cover and then press the Feed button to resume printing.
6. The printer is paused.
   • Press the Feed button to resume printing.
7. The printhead is over temperature.
   • Printing will stop until the printhead cools to an acceptable printing temperature. When it does, the printer will automatically resume operation.
8. FLASH memory is not programmed.
   • Return the printer to an authorized reseller.
9. The printhead or motor has had a critical failure.
   
   • Return the printer to an authorized reseller.
10. The printer is defragmenting memory.
    Caution- Do NOT turn off the printer power during defragmentation. Doing so can damage the printer.
    
    • Defragmentation is a normal operation of the printer – necessary to manage the memory space for optimal use. The printer will defragment its memory both after a factory default and when the printer detects that a defragment is required.
      When the printer is in this condition, allow it to finish defragmenting. If this warning occurs frequently, check the label formats. Formats that frequently and repeatedly write to and erase from memory may cause the printer to defragment often. Using formats that avoid frequent and repeated memory write/erase event will minimize the need for defragmentation.
    • If this warning condition does not go away, contact Technical Support. The printer
      requires service.

Printing a configuration label

To print a configuration label, press and hold the Feed button on top of the printer until the green status light flashes one time. Let go of the button and the printer will print a detailed printer configuration status label. 

Overview of Power on/off modes and flash sequences

The following tables show an overview of the Zebra GK420d "Power on/off" modes and flash sequences. These are used to print configuration labels and reset and calibrate the printer.

The overview is meant as a quick reference for customers who are already familiar with the flash sequences. If you are not familiar with these, we recommend that you read the full user guide.