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Lexmark X792

Lexmark X792

121.36 Fuser Error message

Issue description

The ‘121.36 Fuser Error’ indicates a cold start of the fuser assembly at or below 10 degrees Celsius or 50 degrees Fahrenheit.

Note:  10 C/50 F is outside of the specified operating temperature range for the Lexmark C792 and X792 Series MFP's.



Although the 121.36 is a service error, the printer typically does not require service. The printer posts this error if its internal temperature is below the 10 degrees Celsius or 50 degrees Fahrenheit mark. Before attempting to power on the printer, therefore, allow it to acclimate to the specified operating environment (for example, 15.6 to 32.20 C/60 to 90.00 F).

If the printer has been acclimated and the error persists, perform the following steps to test this.

Note:  The images used show the Lexmark C792 models. However, these directions also apply to the Lexmark X792 models.


  1. Verify if the printer/MFP has acclimated to the specified operation.

    Air Temperature – Product Operating15.6 to 32.20 C (60 to 90.00 F)
    Air Relative HumidityRelative Humidity 8 to 80%
  2. Power off the printer/MFP and unplug the power cord. Wait at least 30 seconds and then plug the power cord directly into a grounded outlet.

    Note:  This step is especially important if the 121.36 error occurs intermittently. Power strips, surge protectors, extension cords and uninterrupted power supplies (UPS) can trigger a false 121.xx error. This is true even if the printer has worked on this surge device previously. If this is not possible, confirm that the power strip is switched on and functioning correctly.

  3. Power on the printer/MFP again to see if the error persists. If the error is still present, document the exact error message and perform the next steps.

  4. Power off the printer/MFP completely and disconnect the power cable from its power supply. Then open the left access door assembly.

  5. Remove the fuser assembly by pulling down the two fuser latches and pull the fuser unit toward you.

    CAUTION—POTENTIAL INJURY:  The inside of the printer/MFP may be hot. Allow it to cool before continuing. Also, do not touch the center of the fuser unit. Doing so damages the fuser.

  6. Check for any broken or loose parts on the fuser assembly. If damage exists, a service call is required to resolve the issue.

  7. Reinstall the fuser into the printer. Close all doors and covers completely.

    Note:  After inserting the fuser assembly, push up the handles (1) and then push up the tab under the right handle (2).

  8. Power on the printer/MFP again.

    Did this clear the error?

    • Yes: Issue resolved.
    • No: If the issue returns, please contact Lexmark Technical Support or a local authorized service provider for additional assistance.


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