Diagnosing AC that won't run

Please give me some basic guidance on diagnosing home AC system. The display on the electronic thermostat went dark, but the batteries aren't dead. The on/off switch on the thermostat can still start the air handler in the attic, but the outside compressor won't run. The breaker did not trip off. There was a lightning storm. What can I do before calling the repairman? Thanks. -B
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B on 6/10/05 8:16 PM wrote:

Start by shutting off all electricity to both units at the breaker. Wait about 15 min. and reset the breakers. See if anything changes.
You might also have someone turn on the unit while you are outside near the outdoor unit. If you hear a clicking sound call a service person. If you hear no sound there is probably a problem with the wiring from the inside unit to the out....call a service man.
I am not a repairman and did not sleep at a Holiday Inn Express last night. This did however happen to me today also.
Mine was a bad time delay on the outside unit. Ended up it was not even needed due to my thermostat being digital. At least that's what the service man told me : )
My guess is the storm caused the problem whatever it is.
Good luck
bmickey9
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"B" wrote
<snip>

Pray
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Good start. Step two is check your bank balances.
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Well, you could check for power at the compressor. Since the T-stat switches run the air handler, that's got power.
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This is Turtle.
i would take the batterys out of the thermostat for 4 hours and then replace them with new batterys in the 4 hours later. During this 4 hours , i would also turn the breaker off to the furnace / air handler to add another check on it too. If after 4 hours with no high volt power and battery power. it will not work, i would say the odds of a bad thermostat would be good but I will say this. I can't see it from here and it could be anything.
TURTLE
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First I would jump out the T-stat wires and see if the compressor comes on (make sure you jump the correct wires). If it does come on, then you know it's the T-stat. The on/off fan switch will still work the air handler as it's just a regular switch integrated in the T-stat.
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I gambled and bought a new thermostat and that fixed it. Thanks everybody. -B

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