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avabean 01-07-2013 08:08 AM

a/c humming
my a/c outside is making a humming noise and I do not have it turned on in my house?

rrolleston 01-07-2013 08:36 AM

Did you also try turning off your ac disconnect outside?

joecaption 01-07-2013 08:38 AM

Can be a bad contactor.

Doc Holliday 01-07-2013 08:42 AM

If you mean the outside condenser is humming although you don't have the thermostat set on call for cool (when was the last time you did have it on cool?) than it could be a combination stuck contactor (allowing power to get to the capacitor) and/or (if a single leg contactor and one leg of 120 volts is constant) simply a bad capacitor.

What kind of condenser is it? Is it a heat pump? Does it work when you turn it on?

Billy_Bob 01-07-2013 09:06 AM

"Heat pumps" use the outside unit for heating. Is it a heat pump?

And they are making these very efficient lately. If it is just humming but the fan is not going, that could be a normal "minimal heat needed" operating mode. Write down the model numbers and call the manufacturer or look at their web site for an owner's manual - which should explain various modes of operation.

dmxtothemax 01-07-2013 05:01 PM

Could be a noisy power transformer used for control circuits !

fa_f3_20 01-07-2013 08:14 PM

If it's a heat pump, and it has one of the old mechanical thermostats, it's normal that sometimes these thermostats apply power to the reversing valve even though no heat or cooling is being called for.

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