Whe the a/c first goes on, it blows 58 degree air and begins to cool the house. (I hung a digital thermometer on the overhead vent.) If the house isn't too hot, it gets cooled down properly and the a/c turns itself off. If the house is hot, the a/c begins to blow 58 degree air, but after a while (maybe an hour or so), the fan continues to blow, since the thermostat is still calling to cool more, but the compressor turns off. All the while, I thought the compressor was still going, because air was blowing out of the vent, but the air was 74 degrees.
Yesterday, I turned the a/c on at 2 pm, and the house began to cool with 58 degree air coming from the vent. The tech arrived at 3:15 pm, and just at that time, I showed him that the vent air was now blowing at 74 degrees. He went outside to the a/c unit, and noticed that although air was blowing out the indoor vent, the compressor was not running as noticed by the fact that the fan on top of the unit was not running. He measured all the amp/volts at the two main capacitors (start and run capacitors) and all was fine. He measured the freon, and it was up to capacity. He then measured the temperature of the compressor, and it was HOT, at 149 degrees. He called back to his company and also to the American Standard, the a/c manufacturer, for advice/trouble shooting. All were baffled.
He then took the garden hose and ran water over the compressor cooling fins, and the compressor started right up and the vent air went from 74 to 71 degrees in a minute, and continued to decline. He surmised that the compressor was overheating and was shutting down, as it should. But, no one knows why the compressor gets so hot. The outdoor temperature was only 80 degrees yesterday. Even if the outdoor temperature is 75 degrees, the compressor gets hot after running for a while and shuts itself off.
The a/c unit is an 18 year-old American Standard model 7A2042A100A1, R22, used to cool a 1700 sq. ft. single story home in the Sacramento area. This is my dad's house, who passed away in late 2013. Beginning in 2012, he used to call me up to figure out why the house didn't cool properly. We had techs out, and they replaced this and that, but still no luck. I replaced two thermostats, thinking that may be the issue, but still no luck.
A month ago, when the tech thought the problem was with the a/c fan, because it was VERY noisy, he replaced the fan and capacitor for about $500. But, warm air still blew.
So far, the tech can only explain this by saying that the unit is old, and just doens't run as efficiently. While I can buy this, I don't know why this would be. Anyone?
At any rate, to replace the compressor is about $2500, which I could do, as it seems everything else is running fine, and especially since I've just replace the fan/capacitor. To replace the entire unit is about $4500, but they suggest that if I replace the entire unit, I should also replace the perfectly running furnace, since a new a/c unit uses the newer 'freon', and they like to match that with the furnace. I don't understand this. But, to replace both a/c and furnace is about $10,000. The a/c unit is about a 3.5 ton unit. I prefer to get by with the $2500 compressor, as I don't know how long I'll keep the house.