H4-00 The Sharp Copier AR5127 displays "call service H4-00" and won't go further than that

H4-00 on Sharp means that the temperature inside the printer is too low. That is usually the fuser lamp, and rarely the temp sensor.
When this happen you need to have the fuser unit replaced, if that does not fix the problem the technician will replace the temperature sensor.

H4 Heat roller abnormally low temperature

Check blinking of the heater lamp
with SIM 5-2.
When the lamp blinks normally:
Check the thermistor and the
harness.
Check the MCU PWB thermistor
input circuit.
When the lamp does not light:
Check for heater lamp
disconnection or thermostat
disconnection.
Check the interlock switch.
Check the power supply PWB
and MCU PWB lamp control
circuit.
Clear the trouble with SIM 14.

Entering the simulation mode
Perform the following procedure to enter the simulation mode.
Clear key ® Interrupt key ® "0" key ® Interrupt key ® Main code ®
Start key ® Sub code ® Start key