A H4 error means “It is the fuser, but sometimes it is just a false code”, caused by a hiccup in your power supply.
SHARP AL-1642CS Engineers Code for clearing a H4 error (maybe others also)
------------------------------------------------
PRESS: Clear - exposure - clear - exposure = the LED display will turn off.
PRESS: # of copy keys until you have 14 displayed.
PRESS: Enter.
------------------------------------------------
Joides
April 2007