Air Conditioner Repair Story
I am not a professional repair person but thought I might pass on my recent experience "debugging" my home central air unit. Basically, I came home and the central air was blowing warm air instead of cold. I checked the outdoor central unit and it was deader than a door nail. A quick check of the breakers revealed nothing wrong. I next checked the thermal overload breaker on the back of the unit. It was tripped. After resetting the thermal breaker, the compresser started up but the cooling fan did not. After the compressor ran about a minute, the thermal breaker tripped again. The fan was the problem. Next I got out the voltmeter and checked input voltages to the fan's on/off relay. Looked normal. Next I checked voltages coming from the relay to the fan. No juice was getting to the fan. Then I noticed half of an earwig lying next to the relay. On a hunch I cut power to the unit and stuck a stick between the relay contacts. There was the other half of the earwig! After turning on power and resetting the thermal breaker, the fan started rotating, but very slowly. I noticed the relay contacts were jittering and arcing a bit. Using a stick I pushed down on the relay arm. The contacts really started arcing and smoking big time for about 10 seconds and then stopped. At the same time the fan resumed full speed. I figure there must have been enough earwig pieces burned onto the contacts to prevent full closure. Applying pressure burned them all away. I must admit, this is the first debugging I've done where the problem turned out to be a real bug.
Answer:
Here in Texas, we have that problem with fire ants. Fire ants crave beryllium (in the beryllium copper contacts) and appear to be able to pick up electric fields. I had to scrape massive balls of fire ants out of my contactor several times before I was successful in eradicating them from my yard. Of course, I probably need to get a new contactor, now. It's probably half eaten...what is real fun is scraping them out of outlets.