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 No 24v at Compressor Contactor
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10 Posts

Posted - 06/22/2018 :  11:35:28 AM  Show Profile  Reply with Quote
There is no 24v in the low voltage line at the outside compressor that is needed to connect to the contactor. The A/C is set on the thermostat inside and the blower comes on and runs but the compressor does not since there is no 24v signal at the compressor.
I cannot see where the low voltage line running to the outside compressor is connected to the controls at the furnace. I am still looking for that connection so I can tell if the lack of 24v is due to no signal from the control or if the long low voltage line is broken somewhere.
I have a very lightly used Lennox G20-E unit that is a 1992 model that is in good condition otherwise. This problem just surfaced last week.
Any ideas where I should determine why the missing on the 24v low voltage line?
I measure the BCC thermocouple voltage of R to Y as 5v. Also the R to Ground is 26v and the Y to Ground is 20v taken with the blower running.


5989 Posts

Posted - 07/06/2018 :  08:34:08 AM  Show Profile  Reply with Quote
"R" is routed to the thermostat and then the thermostat sends the voltage back to the "Y" terminal upon a call for cooling., Inc. is an Independent Lennox Dealer providing a national parts distribution resource for Lennox parts since 2002. The Cozy.Support team does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
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