C6400 6000 on Kyocera Mita KM1500

Almost all kyocera Mita products display error message C6XXX whenever a problem is detected in fixing temperature or fixing unit. C6000/C6200/C6050 and C6400 all are related to fixing unit. Service manual states that possible causes are as below:
C6000 & C6050

• Poor contact in the thermistor connector terminal.
• Thermistor installed incorrectly.
• Thermal cutout triggered.
• Heater lamp installed incorrectly.
• Broken heater wire.

C6020

• Shored thermistor
• Broken heater control circuit on the power supply board.

C6400

• Poor contact in the connector terminals. Check the connection of connectors CY7 on the engine board and CN2 on the power supply board.
• Defective power supply board.
• Defective engine board.

Sometimes only an unstable power source is the cause of these error messages.
How to reset:

1. Press the Stop/clear (red) key, Start (green) key and the left copy exposure key in the order presented and hold them down.
2. Release the keys and than press Stop/clear key again (within few seconds).
3. Using the copy exposure adjustment keys or the Zoom +/- keys go to mode U163.
4. Press the start key.
5. If prompted (Im not sure) confirm that you want to reset the fixing data.
6. Here you go.