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Old 05-14-2016, 12:24 PM   #1
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Please help ac outside unit not running..


Our thermostat comes on, the air handler blows, but the outside unit does not come on. We tested the capacitor, its fine. We replaced the single. Pole contactors with a double pole, everything seems to test fine but the fan and compressor don't come on. When we manually override the contactor it will run but blows hot air inside.

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Old 05-14-2016, 12:33 PM   #2
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Re: Please help ac outside unit not running..


Is it a heat pump?

Post brand and model #.

Do you have 24 volts AC at the contactor coil?

If it is a heatpump and you press the contactor in and the reversing valve is in heat mode you will get heat. Need to see if the thermostat is sending 24 volts on the Y wire to the outdoor unit and contactor. Check between Y and C out there or at the furnace.

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Old 05-14-2016, 01:37 PM   #3
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It's a Trane split system 2TWB
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Old 05-14-2016, 01:39 PM   #4
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Getting 24 volts at the coil. When manually pushing in the contactor heat comes out
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Old 05-14-2016, 01:58 PM   #5
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Re: Please help ac outside unit not running..


It looks like a heat pump which I don't see many of where I am.

If you are getting 24 volts across the coil it should pull in unless the contactor is sticking. Need to check across the coil and NOT to ground or you can get fooled.

However the reversing valve should be in the cooling position as it gets a signal at the same time to move it to cool ( unless it is a brand that does not, Rheem I believe ). If it is getting the signal and you push the contactor in it should cool.

Check back here later as there may be some techs here who know that unit better.
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Last edited by yuri; 05-14-2016 at 02:01 PM.
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Old 05-14-2016, 01:59 PM   #6
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Thank you
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Old 05-14-2016, 02:02 PM   #7
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Re: Please help ac outside unit not running..


Yur Welcome.

My comrade Beenthere knows Trane and there will be others here within 8 hours or tomorrow.
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Old 05-14-2016, 02:13 PM   #8
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Re: Please help ac outside unit not running..


What's the voltage across the coil?
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Old 05-14-2016, 04:01 PM   #9
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24 volts
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Old 05-14-2016, 05:27 PM   #10
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Re: Please help ac outside unit not running..


If there is 24v across the coil of the contactor, and it's not pulled in, then it's dead. Replace it.

Cheers!
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Old 05-15-2016, 10:34 AM   #11
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I replaced the contactor and still same issues. Is it possible the contactor is faulty or can something else cause this?
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Old 05-15-2016, 10:52 AM   #12
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Re: Please help ac outside unit not running..


Are you measuring 24 volts at the contactor or at the connections coming into the condenser? The contactor you purchased has a 24 volt coil?
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Old 05-15-2016, 10:55 AM   #13
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At the contactor is 24 volts and the coil is a 24 volt coil.
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Old 05-15-2016, 11:09 AM   #14
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Re: Please help ac outside unit not running..


if it has 24 volts at contactor and is not pulling in then the contactor is faulty. I find the odds of having your old contactor and new contactor bad are not too likely though. You mentioned earlier when you engaged contactor unit was producing heat. So I am assuming you are getting 220 volts. It's hard to tell over the internet but I have to ask so I can understand. When you are measuring 24 volts, you are measuring with a lead on each side of coil and not to ground right?
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Old 05-15-2016, 11:14 AM   #15
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220 coming in but 24 at ground.

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