Question for AC guys

[Gerald C. Wilcox]

As I checked a central air unit today, I have a couple of questions. When I activated the thermostat, I went outside to check out the condensing unit. The compressor came on, and within a minute or two the high pressure line was very hot, the low pressure line was cool. The cooling fan did not activate. I shut it down after a couple of minutes. The unit was an Evco about 3-4 years old. Is this normal for the fan not to come on right away or begin to cycle? The compressor sounded like it was trying to prime itself, and then appeared to change rpm. I was told that it worked and that it has been operated this year. What say ye?

[Bruce A. King]

The airhandler could have a bad capacitor for the fan motor.

[Charley L. Bottger]

Originally Posted by gwilcox

As I checked a central air unit today, I have a couple of questions. When I activated the thermostat, I went outside to check out the condensing unit. The compressor came on, and within a minute or two the high pressure line was very hot, the low pressure line was cool. The cooling fan did not activate. I shut it down after a couple of minutes. The unit was an Evco about 3-4 years old. Is this normal for the fan not to come on right away or begin to cycle? The compressor sounded like it was trying to prime itself, and then appeared to change rpm. I was told that it worked and that it has been operated this year. What say ye?

I say ye have a condenser fan motor that has crapped out and needs replaced. The compressor will run for just a very short period and then kick out on internal overload. This will drastically shorten the life expectancy of the compressor if allowed to operate in this condition.??????

You used the term cooling fan, to me that would be the indoor blower motor and I assume you are referring to the outside fan motor. Is this correct.

[Gerald C. Wilcox]

Yes, that is correct. I should have said the fan motor on the condensing unit. The compressor never kicked out, and I thought the unit smelled hot so I shut it down.

[Charley L. Bottger]

Originally Posted by gwilcox

Yes, that is correct. I should have said the fan motor on the condensing unit. The compressor never kicked out, and I thought the unit smelled hot so I shut it down.

The compressor and discharge line would burn your hand if touched with no fan running as the discharge pressure would have exceeded 400 PSIG if the outside ambient was in the 90's. and trust me the compressor would have kicked on internal overload if you had not shut it down you did the right thing.

The fan should have started running this time of year at the same time the contactor pulled in even if there was a speed control or a head pressure control installed which was probally not likely.

[Gerald C. Wilcox]

Thanks Charlie, I think you hit the nail on the head! I could not hold my hand on the high pressure line for more than a moment, after only 2-3 minutes, and the ambient temp, was in the low 90's. I'll call it out as needing service.

[David A. Andersen]

I'll call it out as needing service.

I'd call it needinf "repair"!

By the way, if for the fun of it you wanted to know if it was the cap or motor, spin the blade with a screwdriver (not your finger). If the motor runs, it's the cap.

[Gerald C. Wilcox]

Thanks for that info David