Compressor runs whenever 'fan' is on?

Problems related to residential installations.

Compressor runs whenever 'fan' is on?

Postby riekls » Wed Aug 08, 2012 4:50 pm

I'd like to be able to run my furnace fan without the ac compressor on, every other house i've been able to do this. I've tried 3 different thermostats and on any of them if i turn 'fan' on the ac compressor turns on also.

I've traced the wiring and everything appears right. The fan control (g) is connected and not jumpered to anything. Why would the ac compressor turn on when activation is sent down the green wire?
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- Compressor runs whenever 'fan' is on?

Postby Freon » Sat Aug 11, 2012 11:20 am

It shouldn't! Check the connections at the air handler. The Ac wire from the thermostat's Y terminal should be connected to the Y terminal at the air handler. Also connected at the Y terminal at the air handler should be 1 wire going outside to the condenser contactor. See if someone has added any jumper between the G and Y terminals at the air handler. You might also check the thermostat to see if when you set the Fan to On it's also powering the Y terminal. I've never heard of that happening so I suggest you read the thermostat literature to be sure you don't have a unique 'feature'.
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