Zebra gk420t blink red/green - Zebra GK420 Thermal Printer

Do a factory reset on the printer.

Check you printer driver settings if you are printing using it.

Print head is toast. Need new one.

Seems its loosing calibration, try to reset to factory defult setting and it will calibrate with the labels that have at the moment. Please check settings at windows drivers (should be set up at Thermal transfere if using ribbon otherwise Direct Thermal if not using ribbon.
That issue can happen aswell if when sending a job to the printer with wrong settings, it will overrwrithe the previose settings of the printer.
you can untick the setting " use printer settings" at drivers as well.
if you need diferent driver go to www.seagulldrivers.com - this driver let you to resett printer to factury defaults. Hope it helps.Paulo.

It could be anything. wrong type of labels or label stuck on the sensor of the printer. Try to re-calibrate the printer.

From the owner's manual:

Alternately Flashing Green and Red: Needs Service 8

8. FLASH memory is not programmed.
• Return the printer to an authorized reseller

You can find the complete owner's manual on Zebra's web site.

The problem that you are facing can be resolved by doing a reset on the printer and then setup the printer on the network again. This will resolve the issue.

Check their website. It should let you download the user's manual after you've logged in.

http://www.zebra.com/id/zebra/na/en/index/products/printers/desktop/tlp2844z.4.tabs.html


I work with these at my work-work, and the manuals are pretty handy to have!