I'm having a strange problem with the A/C (a heat pump). One night
near the end of last summer we had some lightning. The next day our
upstairs A/C started blowing hot air so I called the A/C repair. They
topped off the coolant, replaced the capacitor. They also said that
the thermostat was calling for the heat strips, so the thermostat was
replaced. The A/C was working. A day or two later the A/C was not
blowing cool air. I determined that the compressor was running but
the fan compressor was not turning. But the problem was intermittent.
Anyhow they came back out and replaced the fan motor. It worked for
about two weeks, but it was always noisier than the old one they took
out. Then it quit working some of the time, but the problem was again
intermittent. I had a hard time getting the fan to quit turning when
they were out here, but finally it happened. They said that the motor
they had put in was defective, and they put in another one. This
motor was quieter than the one they replaced. This was near the end
of summer, so soon we didn't need cooling anymore. They made a total
of five trips.

Skip to about two weeks ago, once again cooling is needed. It was
working, but I heard it make a loud noise, and the compressor fan
stopped turning again. (One of the copper tubes also gets pretty hot
when this happens.) This was in the middle of the afternoon. I
thought that maybe the fan had gotten too hot or something. I turned
it off and then tried it about six hours later, at night. The fan
would not start turning. I waited until the night of the next day and
tried it again - the fan would not start. Then it was cool for about
a week and cooling was not needed. At this point I thought that it
was never going to come on and I was going to call the repairmen
again, but I was waiting for hot weather again. But then my daughter
turned it on a few days ago and it has been working ever since.

That is a shortened version of the story. I also tried some
experiments. It is on a setback thermostat, which was set to allow
the temp to go to 81 during the day and then cool down to 79 at 5PM. I
thought that it may be trying to do too much work in the process and
overheating. I tried keeping it set on 79 to reduce the strain at
5PM. Sometimes it would work, others it would quit. I tried keeping
it on 77 with the same results - sometimes the fan ran, sometimes it
did not.

What can be the cause of this behavior? Keep in mind that we had some
lightning just before the problem started so it may be electrical, but
the thermostat has been replaced and the motor has been replaced
twice.


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