Hope this helps:-
C0500: Warming-up Failure
C0510: Abnormally Low Fusing Temperature
C0520: Abnormally High Fusing Temperature
Relevant Electrical Parts
Fusing Roller Heater Lamp H1
Fusing Roller Thermistor TH1
Fusing Roller Thermostat TS1
Fusing Roller Heater Lamp Fuse TF1
Side Cover Interlock Switch 2 S3
Power Supply Unit 1 PU1
Copier Guy
October 2008