I have had to manually defrost this unit a few times... now it's time to fix it. I thought I had it once when I discovered the control board was never programmed with the code initially. Now I want to force it to defrost or run a diagnostic with out cutting out each component. I do not have the tech sheet, but have figured most of it out by watching tube. When I do a forced defrost I can get it selected to short program but nothing happens. In the diagnostic section the defrost test should show eithe a C or a 0 it shows nothing in that display. I have even sprayed the thermostat with compressed air and frosted it pretty good still nothing.. Help.