a/c thermostat sutting down

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  #1  
Old 07-02-11, 08:14 PM
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Smile a/c thermostat sutting down

Howdy all, need some help with and A/C thermostat issue. My thermostat is losing power and shutting off then it comes back on. I have troubleshot the breaker and it is fine, both the fan and compressor work fine, the small line from the compressor is cool to the touch, and I washed the coils. What is happening is the thermostat turns on the A/C, runs sometimes for 15 minutes, sometimes 5 and quits. Thermostat shuts off no power. then it comes on by itself. I checked the 24vac after it shuts down and I am losing power to the thermostat. After about 2-3 minutes or so 24vac returns. I cycled the breaker outside and it turns the stat off and on as I flip the breaker. Anyone have any experience with this problem? Thanx Dave
 
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Old 07-02-11, 08:38 PM
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Check the transformer in the air handler.
 
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Old 07-07-11, 02:01 AM
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I didn't see a return post from the direction that was given you. I have a digital thermostat and I was told that if the battery goes dead that this would affect the operation of the AC/Heat of the unit. That is if it uses batteries. Just a thought.
 
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Old 07-07-11, 07:40 PM
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Originally Posted by SteveA View Post
I didn't see a return post from the direction that was given you. I have a digital thermostat and I was told that if the battery goes dead that this would affect the operation of the AC/Heat of the unit. That is if it uses batteries. Just a thought.
But.....some thermostats with batteries only use the battery for back-up to retain the program when the power is off and for the backlit display. I detest thermostats that need batteries for operation, but they are cheaper when you buy them.
 
  #5  
Old 07-08-11, 12:10 AM
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No so...

Most digital thermostats use batteries to run the thermostat and all of its functions. That includes the relay on the thermostat that closes and runs the ac unit. If the batteries are weak then they don't have enough power to hole relay closed. Some of the better thermostats use the common "C" wire to power the thermostat off of the 24 volts on your transformer and batteries for backup in case AC fails. If your thermostat does not have a c or common terminal with a wire attached then batteries are running the thermostat all the time. If so than you should use really good alkaline batteries not dollar store or rechargeable batteries. And change them at the start of the cooling and again at the start of heating season. You don't want to wake up without heat from dead batteries.
 
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