I have a payne air handler(14 year old)... the 5 amp fuse is blown. I replace the fuse and it blew again... I noticed that the 220 ground is corroded and should be cleaned/replaced. Am I at the source of the problem or are the other items to look at be replacing the fuse? Currently nothing works(a/c or air handler)... just a slight hum from the air handler... thanks

Does the fuse blow immediately when replaced, or after system operation is initiated? If you don't have a voltmeter, some trial-and-error may track down the problem. Look for damage to the low-voltage wiring, particularly near the outdoor unit. Hungry rodents will try to eat just about anything.

Thanks for your help!! The 5 amp fuse blows immediately... I took a quick look yesterday and at first glance, things looked OK regarding obvious shorts... I will try taking some voltage readings, but have nothing to compare values to... I will look for any possible shorts or obvious failing components, stuck relays, etc. in both units... was able to find an article mentioning that a bad 220 ground on the air handler could cause the fuse to blow... the wiring is 30 years old and the ground wire is green with corrosion and may not be doing it's thing... I'm about ready to get some parts(fuses, wire, ground lug, etc) and clean up that problem. I'll will also give the air handler/compressor unit a good visual and try to take some voltage readings... hope it's something simple! Thanks again...

One thing I forgot to mention was that the defrost cycle seemed to be coming on frequently over that past week. I'm not sure whether I was just catching it at the right time or not... thanks again

Well, it's only 2:30am and it's putting out heat without blowing fuses! (and the first time too!! ) made my day... all it has to do is keep running... I cleaned up the ground and replace the lug... plus checked the inside and outside unit as best I could. The logic card on the compressor unit had a few webs on the back, but otherwise all wires and connections looked good. The inside unit, I cleaned the ground problem by shorting the wire down to clean copper, plus replacing the lug... it was in sad shape... also gave it a good cleaning while I was as it. The squirrel cage was had to clean(any recommendations on the best way to clean one?) all other wires, connections, etc. looked fine. In all this work I came up with another question I need to resolve... I'm not sure what the amp rating were on the old(first) unit... it had two 35 amp cartridge fuses on the compressor unit( the new unit says max of 40 amp) which seems to be fine... the indoor unit has two 60 amp breakers(done with the first unit) The main panel has a double 40 amp breaker for the outside unit and a double 60 amp breaker the inside unit... the problem is that I can't find any amp ratings for the current inside unit... I think the breakers for the air handler maybe over stated and may not trip when needed... the compressor/outside unit is a payne 812an036-a and the inside/air handler is (from what I can tell a carrier fc4bnf036)... I know there are sisters, but I can't find any payne literature or any info on the labels stating either payne or the amp ratings... I ran into this because the 220 cable for the air handler is 4gauge and all I could find was 6... (6 being rated to about 50 amps or so... I didn't want to change the cable to 6 gauge for safety reasons even though the wire inside the air handler that the cable attached was 10 gauge... where can I find the real rating the fc4bnf036 unit (air handler) so I can change out the breakers, if needed... thanks .hope this makes sense...

I meant shortening, not shorting...
Sorry for the other typos, etc... guess I'm tired! Haha

The rating label for the auxiliary heat package should provide the correct ratings for circuit protection. These override the standard fan coil ratings when a heat package is installed. If the heat package has 2 breakers, the unit should be served by 2 circuits/panel breakers sized appropriately. Oversized wiring is OK, but undersized is a no-no. Sounds like you have some issues there. If the blower assembly is dirty enough, imbalance & vibration will result. The most effective way to clean it is to completely remove & dis-assemble it, then thoroughly spray the wheel & housing with water. Use a vacuum cleaner on the motor. Pay close attention during dis-assembly to assure proper re-assembly. Take pics along the way for reference if you so choose.

Where are the fuses on a payne air conditioning?