AC compressor

[ransley]

The air handler does work, and when I push in the relay on the outside compressor unit it runs, so I guess next I check for 24v to the compressor relay?

[jamesgangnc]

e quoted text -

On most of these the 24vac power comes out from the air handler to the outside unit. It's how the insde unit turns on the outside one. So yes, sounds like you should troubleshoot the 24vac. Start at the outside relay and work back to the air handler checking for 24vac when the inside unit is running in the cooling mode. The 24vac wire should be color coded so you can find it at the inside unit if you have to go back that far. Obviously if you have 24vac at the outside relay then you have a bad relay.

[jamesgangnc]

ide quoted text -

I forgot, to be safer you can usually turn off the outside unit while troubleshooting the 24vac. The inside unit supplies the 24vac.

[Colbyt]

The air handler does work, and when I push in the relay on the outside compressor unit it runs, so I guess next I check for 24v to the compressor relay?

The only thing controlling the 24 volt system before it gets to the outside unit is thermostat. Are you sure it is good? Find the two wire cable and test for 24V there first.

Many of the 1995 and later models have a low pressure switch wired into the

24 volt system inside the condenser unit. This part might also be the problem. Just mentioning these two things BEFORE you run out and buy a non-returnable contactor.

Follow the 24V wires and test for current after each part. Entry point, low pressure switch and at the contactor. Actually working that in reverse is the smarter way to do it. I just wanted you to see the path.

[HeyBub]

Ah, right. I forgot.

[HeyBub]

Yep. It's either not getting the 24v OR unable to use the voltage cause the relay itself has given up the ghost, taken a dirt nap, singing in the heavenly choir, or passed this way only once to brighten our lives, provide endearing memories, and let us chill.

[Oren]

I know... keep one hand in your pocket!

What do I win?

[Malcolm Hoar]

Umm, messy underwear?

[cjt]

Squirrels and other critters have been known to enjoy a meal of insulation.

[Stormin Mormon]

Happens to the best of us. We all forget something or

[The Daring Dufas]

OK, I found several links for you with colored pictures and one even has a little video. The information is good and will give you several excellent images of what the parts look like and info on what they do.

================================================

================================================ TDD

[The Daring Dufas]

The low voltage wires going to the contactor coil are usually yellow in color, sometimes one is blue which is the common.

TDD

[The Daring Dufas]

It's not unusual for wires to move or rattle inside a conduit even if the wire is properly sized for the load. The starting current of an AC compressor can easily be several time the run current of the whole unit. Wires can and will dance under the right set of circumstances.

TDD

[The Daring Dufas]

It may turn slowly while making an unhappy whirring sound or just hum angrily. HVAC equipment can get emotional at times. 8-)

TDD

[The Daring Dufas]

If it's a combo capacitor with 3 terminals, the top will pop up when it fails, killing both the fan and compressor.

TDD

[The Daring Dufas]

Did you happen to run a weed eater around the condensing unit? I see that activity cut the control wire to the condenser quite often.

TDD

[The Daring Dufas]

He did mention that it's a 13 SEER unit and it may very well have a low pressure cutout switch. The builder grade units, even the newest of them don't have a factory installed low or high pressure cutout.

TDD

[jamesgangnc]

You're an idiot. Wires do not move in this example.

[The Daring Dufas]

I only have four decades experience in the field and I see it all the time. In an industrial environment I've come across it a lot where there are a numerous high current starting loads for motors. The wire can actually change length under heavy load. I've seen insulation rubbed of a wire because of this movement. The OP can hear the #10 wires jump inside the conduit when his AC unit stars. When you get your PhD in know-it-allogy, come back and call me names.

TDD

[jamesgangnc]

Go ahead give us the science behind it then?