U4 - 5328 xerox

H2 is a termistor open....you have to reset it if it works ok if not you have to change the termistor..

enter service mode c - auto -c auto than enter 14 and start .....if the code goes it is ok if not change termistor.

did u check your fixing unit, termistor termostat didi u clean and reset 47 or 35 mode

This error appears when you have problems with TERMISTORS in fusing unit. You have to replace termistors if you can't reset the service call condition in service mode.
pifonski

A H4 code is a problem with the fuser unit. That xerox is a Sharp copier. You may have a blown thermister or thermal fuse or a fusing lamp. You may need to repair the problem before you can clear it. I believe the code to reset it is in service mode SM 16

push clear 1 0 7 and the clear/stop (one at a time in order) key this enters service modes, turn machine off/on (rocker switch) this will clear your code. this is a fusing code (low temp) so make sure no paper is in the fusing unit (hot, black and orange rollers)

press clear (yellow) and press 1,0,7 and press and HOLD the stop button 5 secs. (red) press 1 when u see the copy sp mode and press 7 (datalog) and press ok, look for the sc/ jam counter reset. press the execute 2x. turn of the machine in the main switch (orange switch on the lower front side) the shortcut mode is by pressing 7807 na press execute

U6 code means that you have a problem with the exposure lamp or exposure lamp circuit working properly.Hold down the 0(zero) key while turning the unit on and punch in the codes 20 start 3 this will enable you to clear the code unless you have a permanent problem where a part has to be replaced

call service --- possible bad thermistor (fuser)
could over heat

Try changing the termistor, must be damaged. and reset by total clear, 107 and press and hold the clear stop key more of 3 seconds.

Turn power on and within 4 sec.press the following sequence;clear,exposure,clear,exposure.The screen will go blank.Enter '1' and '4' then hit print.turn off. This will reset H4 if the fuser has no problems such as a bad fuser lamp or thermal fuse.And yes it,s worth fixing with the right guy working on it!