AC won't turn on. What to check next?


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Old 06-07-11, 09:23 PM
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Question AC won't turn on. What to check next?

Hey everyone,

Came home today to a hot house and a central air unit that will not turn on. I have checked the obvious things like circuit breakers and called the power company to make sure the Saver Box was not malfunctioning. Also the thermostat is working properly, along with the indoor fan by the furnace. (Both of those are brand new as of 12/2010.)

Breaker in the basement is good, breaker outside near the unit has power (verified by watching the Saver Box go off and on, when I flipped the switch.

A call to the power company confirmed that the Saver Box was working properly and was not the problem.

The thermostat says "Cool On" and I can hear the fan running on stage 2 or stage 3. (It normally is on stage 1 to circulate the air)

I opened the AC unit after cutting power to it, and looked to see if there was a fuse or anything else that would jump out at me. I couldn't find anything. On the back of the unit is a red rubber knob that sticks out about a quarter inch and is a tad bit bigger than the cap that goes on an air valve stem of a car or bike tire.

I thought that might have been a fuse, but it doesn't push/pull/turn/etc. Not sure what that is for.

What would be the next thing to check?

Older AC Unit. Montgomery Ward Model #SRM-51220A
 
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Old 06-07-11, 10:05 PM
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check contactor to see if it pulls in upon call for cooling........ if not recheck saver box
 
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Old 06-07-11, 10:24 PM
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Hey hvactechfw,

Thanks for the response. About a half hour ago, I went to the thermostat and tried turning on the AC as low as it would go (65 degrees) and the AC unit outside started right up. It is also kicking out cold air.

I guess now my follow up question would be why would it work now, but not before? Is there a different signal or something that gets sent to the unit when you put the thermostat as low as it can go? I am going to leave it at 65 for tonight, so I can get some sleep. Tomorrow before I go to work, I will return the thermostat to its normal setting and see what the house is like when I return home from work that evening.

Thanks again for your response.
 
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Old 06-08-11, 03:31 PM
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there is no different signal..... it was either in delay before (doubtful) or it was the utility saver box that was keeping it from coming on because of high demand at that time so the utility company sent the signal to shut off a/c
 
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Old 06-08-11, 11:22 PM
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AC was working normally today. Thanks for your help!
 
 

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