Air conditioning - outdoor unit runs but indoor fan not working

Old 09-09-15, 09:47 AM
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Air conditioning - outdoor unit runs but indoor fan not working

Our air conditioning behaves odd lately...Mainly the indoor fan issue I guess...
1) if I turn the switch from auto to on, sometimes the indoor fan runs, sometimes not
2) if in the auto position, the same problem occurs, the indoor fan sometimes runs sometimes not while outdoor unit is working
3)if I get lucky to have the indoor fan running, then it won't stop when the room temperature drops to the desired temp. I got to adjust the thermostat higher to stop it. And then after a while thermostat is calling air conditioning because the room temp is up, only the outdoor unit comes back to run the indoor fan is not back working....

I tried the main breaker, it only worked one time...I cleaned the mechanical thermostat by paint brush... I have not gone to the attic to check yet...

Any advice? Many thank
Old 09-09-15, 10:26 AM
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If you have a voltmeter, set it to AC volts and check between the G and R terminals on the thermostat. When the fan should be off (switch set to auto, thermostat not calling for heat or cooling), you should measure ~24VAC between G & R. When the fan should be running, the voltage between G & R should drop to 0VAC. I would suggest that you start there and see what you get.

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