# Thermostat goes blank and furnace breaker trips when trying to turn on the A\C



## jhutch (Jul 3, 2011)

I have central air conditioning that uses the furnace blower system. When the t-stat sends the signal to the furnace to kick on the A\C you can hear a slight hum then after about 10 minutes the furnace breaker trips and the t-stat goes blank. If I reset and turn the t-stat to fan the breaker will trip immediately. Is the furnace motor bad or could it be the a\c unit outside?


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## kok328 (Jul 3, 2011)

Isolate the two components and see if the indoor blower fan causes the breaker to trip.
If not, then it will either be the compressor or the compressor fan that is causing teh problem.


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## jhutch (Jul 3, 2011)

How do I isolate the two components?


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## kok328 (Jul 4, 2011)

At the thermostat you should have the option to turn the Fan switch from Auto to On.
Another approach is to remove the disconnect outside by the compressor unit and then turn the A/C on.
The disconnect is most likely a grey box about 4"x6" with a cover.  It will either have fuses or a T-handle blade style jumper to complete the circuit.  Turn the power off and then remove whatever convention they are utilizing and then turn the power back on and turn on the A/C.
Your basically looking for a mean of running the indoor blower without running the A/C.
If you have to, you could simply turn the Heat on for a short while to see if the indoor blower fan motor is the cause of the problem.
Most likely, it's the outdoor unit that is the problem.
Good luck and be safe.


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