A couple years ago, I started having a problem with my HVAC. Most of the time I am at home by myself and have no problem with the cooling of my house (in Florida). But when I had friends or family over for a gathering, over the course of a few hours my inside temperature would keep rising, even though the a/c was running non-stop. I complained to my A/C maintenance company (the same ones who installed my system), and each time they would check, calibrate, read temperatures or whatever, and tell me everything was in order.

So, one day I monitored the temperature of the air coming out of the vents when I had several people over with the indoor temperature was rising. I discovered that the conditioned air went through a cycle of blowing warm and blowing cold, instead of consistently cold. I complained again to my a/c company. They checked the system again and found that my compressor was overheating and shutting off, and they replaced it. However, this didn't solve the problem and I complained again. They recommended that I install a new air intake upstairs - but some friends advised me that this made no sense at all since the amount of airflow through the system would not affect whether or not the outside compressor unit would overheat and shut off.

After some more checking with the help of some friends and another a/c professional, I discovered that the full cycle of the problem goes like this:

1. A/C compressor unit turns on per thermostat setting.

2. After running 20 minutes or so (with a number of people in the house, lights on, doors being opened and closed, etc.), the compressor fan motor shuts off (overheated, I believe).

3. Shortly after the compressor fan motor shuts off, the compressor overheats and shuts off.

4. After some more time, the compressor fan motor comes back on (I assume because it has cooled down).

5. After a little bit, the compressor comes back on (cooled off by the fan).

6. Cycle continues steps 2 thru 6.

All during this sequence, the air handler/blower inside the house is running non-stop.

Based on this, I replaced the compressor fan motor (with same model as original), thinking it must be bad. Didnt solve the problem. So, I replaced the start capacitor, even though it tested good, just in case. DidnÂt solve the problem.

And by the way, if I run a water sprinkler outside over the compressor unit including the fan motor, everything works perfectly. If I set the sprinkler to hit just the compressor and fins, the cooling works perfectly but the fan motor does cycle on and off (i.e., it must overheat and cut out).

No one I have spoken to about this has any idea of what else it could be. I think the question boils down to: what else could cause the compressor fan motor to overheat while running?

(These have already been checked: The fan propeller is installed in the proper direction; the coolant charge is proper  not too much or too little; the compressor unit fins are clean. )

Anyone have any ideas?