Payne/Carrier Blowing 3 amp fuses during oper

14:55 ______________________________________________________________________ I have a Payne/Carrier model 394GAW036050AAEA HVAC unit that keeps blowing the 3 amp circuit card fuse during heating operations. I noticed that one of the relay posts solder joints was overheated and desoldered from the board. I resoldered the relay post, replace the filter and cleaned the fan. The unit was extremely contaminated with dust/lint/dirt.The ciruit card looks like it has seen a lot of operational heat. Possibly from overload. Was wondering what could cause this? Maybe a bad start capacitor? Maybe bad components on the circuit card due to overload. I also noticed that someone had crossed the Hi (red) and Lo (black) hookups from the fan to the circuit card. I don’t believe this to be the cause of the fuse constantly blowing because the unit worked okay for the past 2 years and suddendly started blowing fuses. The wiring was corrected to the schematic, but it still blows fuses. Wished I was warm! Replies: yuri “Re(1):Payne/Carrier Blowing 3 amp fuses durin” , posted Tue 15 Jan 17:56 ______________________________________________________________________ The board is probably shot. They will overheat from being coated with dust, poor airflow over them due to plugged air filter. They will die from old age as well. You may also have a short in your 24 volt wiring but it sounds like you need a new board first. Yuri northernfitter “Re(2):Payne/Carrier Blowing 3 amp fuses durin” , posted Sat 19 Jan 22:06 ______________________________________________________________________ I had a carrier in an old farm house where we had been there 3 times replacing the fuse. Cycle it and it would run fine for 3 days. I get the call go out and was pretty sure my reading were off for a second and couldnt find any shorts in the 24v. Take off the board to install new one and meet the field mouse that got cooked to the back of the board. 14years as a service tech in Ottawa and the valley. For furnace manufacturer ratings go to gas-furnaces/furnaces-repair-history-205/overview/index.htm?resultPage Index=1&resultIndex=1&searchTerm=furnace