H4 code flashing. turned it off and back on...still flashing. anything else we could try?

SOURCE: AL 1631 Sharp digital copier

H4 is an indication of a fusing unit heater problem. Most of the time this is a false code caused by power fluctuations or noise.
To reset the H4 condition, press the following key's in sequence and as quickly as possible (with 4 seconds for the first 4 keys)
Press "C" then the far left key (exposure mode) then the "C" key then the far left again.
So in other words C, far left, C, far left
If done correctly the display should go blank.
Now key in 14 as if you were going to make 14 copies.
Now press the print button.
The machine should reset and the code should be gone.
9 times out of 10 this is a false code that pops up due to power surges or noise.
If the code comes back this means you have a heater lamp or thermal fuse (more common) failure in the fusing area and will need service.
Good Luck and Thank You for using Fixya.

SOURCE: h4 error code

H4 00 Content Heat roller low temperature detection
Detail When the fusing temperature is lower than
150C° after 55sec from the start of warming
up.
When the warming up complete temperature is
not reached in 30sec from reaching 150C°.
When the fusing temperature is lower than
100C° after 20sec from ready start.
When the fusing temperature is lower than
145C° when printing."
Cause Thermistor abnormality
Heater lamp abnormality
Thermostat abnormality
Control PWB abnormality
Check
and
remedy
Use SIM 5-02 to check the heater lamp blinking
operation.
When the lamp blinks normally.
Check the thermistor and its harness.
Check the thermistor input circuit on the control
PWB.
When the lamp does not light up.
Check for disconnection of the heater lamp and
the thermostat. Check the interlock switch.
Check the power PWB and the lamp control
circuit on the MCU PWB.
Use SIM 14 to clear the self diagnostic display.