can not get override button to operate on H machine.all other button functions operate;replaced front panel assy already

Try replacing display board behind the front panel.

replaced plasma display & frt panel assy;override button not working

Check all your cables carefully to make sure they are seated and there is no corrosion. Also check the ribbon cable that connects the front panel to the function board. I've seen these get pinched and damage one of the internal wires. If that fails go after the function board itself. Good Luck.

update;took a COMPLETE known working card cage and put into problem machine.to be safe,i did a condo and heat calibration before sending it back out.to my surprise,after hitting set button to save heat cal,i then hit override button and guess what?,went right back to main cal screen just like it should.figured that every time i hit the "override" button,it was working as designed.put it back on the floor in dialysis mode,overide button does not work.Boys at FUSA said try distribution board then try power supply.i just love this "try this,try that" diagnoisis.any help out there on where to go with this/

FUSA loves selling parts! Just a shot in the dark, Since the override switch controls the blood pump in dialysis mode, see if swapping the Pump module out does anything. At this point the only other suggestion is calling in a Priest