My residential central AC unit is acting up. When the thermostat sends a start command to the AC unit, blower starts but the compressor does not start. If I wait a couple of hours and try it again, the compressor starts. So, it is not the power to the compressor. Is there anything I can check to pinpoint the faulty part?

Thanks.
Alan

One thing you can check with a meter is for 24 volts at the outside A/C contactor when the thermostat is in the A/C mode. The signal is used to pull in the contactor to start the outside unit. Without the signal from the inside unit the outside unit will not start.

The problem you have is intermittent and as such could take some time to find.

Possible areas of testing include

Thermostat signal source

Wiring from thermostat to indoor unit

Wiring from indoor unit to outside unit

Low voltage signal power in the outside unit being disrupted by other safety devices in the outside unit. Low and high pressure switches oir time delay modules etc.

One possible cause is that you capicator in not strong enough to start the compressor. It is a very cheep item and easy to change if you know how to protect yourself while working with electricity.

If your unit is less than 15 years old you probably have a duel capacitor in one, it will have three different sets of terminals on the top. One sec will be marked C or com the second will be marked Fan the third will be marked Herm. Remember for sure how you take the wires off and put them back on the same way. If you buy a capacitor make sure that the info on the side matches the old one, it may be something like 45uf 370 volts / 5uf 370 volts.

Now a second thing you can do if this does not work is to get a hard start kit ( I use one called a kick start) it is easy to install, just two spade clip wires to push on. One size of this Kick start fits up to a 5 ton unit.

If my information helps you please let me know.

The compressor has started a last couple of times so I am in the holding pattern. I am going to look into purchasing a new capacitor as a spare.

Thanks for your insight.

Quote:

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Originally Posted by Alanshaw

The compressor has started a last couple of times so I am in the holding pattern. I am going to look into purchasing a new capacitor as a spare.

Thanks for your insight.

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You're welcome, I hope this is the end of your problem but if not send us another message.