FS-4200 C6120 Error Code

[RoyROd]

Hello all, I am currently dealing with a Kyocera FS-4200 that is giving a C6120, Abnormally high fuser thermistor 1 temperature, I've checked the pins and the triacs, replaced the Fuser, the Power Supply Board, and the Engine Board, all with the same result, C6120. Has anyone ever seen this problem before and if so, how did you resolve it? Any help or advice would be greatly appreciated. Thank you in advanced.

[subaro]

Did you install the new fuser as to the service manual instructions below ?. If it is not installed correctly, the fuser will not turn and the machine will detect an over heat condition and code out.

[60/50/45 ppm model]
8. Remove the screw and then remove the
fuser unit forward.
9. Check or replace the fuser unit and refit
all the removed parts.
Caution: when refitting the fuser unit, perform
the following procedures.
(1)Turn on the power switch while opening the
rear cover after removing the fuser unit.
(2)Turn off the power switch after 5-second or
more progress.
(release state of fixing pressure)
(3)Refit the fuser unit.

If you did the install correctly, then check the

10. Fuser thermistor relay PWB
(FUTHRPWB) ....................................... Consists of wiring relay circuit between engine PWB ,fuser
thermistors and cooling fans.
see page 197 of the service manual wiring diagram.
check the continuity of the wiring going from fuser to this board and the connectors if they are in properly.

[RoyROd]

Got it figured out, turns out some moisture had somehow gotten onto the Thermistor relay PWB, rusting and shorting it, I also found something that suggests user neglect.
We changed out the PWB with one we had on hand and bada bing bada boom it came up without a problem, will be having a discussion with customer about this, thank you for your help, I would not have even looked at that PWB without your suggestion.

[subaro]

Got it figured out, turns out some moisture had somehow gotten onto the Thermistor relay PWB, rusting and shorting it, I also found something that suggests user neglect.
We changed out the PWB with one we had on hand and bada bing bada boom it came up without a problem, will be having a discussion with customer about this, thank you for your help, I would not have even looked at that PWB without your suggestion.


My question is why would you not have looked at that pwb. Good troubleshooting would make use of the manuals, electrical schematic drawings and component layout and definitions. Great that you solved the problem.