A/C shutting off before set temperature reached


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Old 07-06-17, 09:20 AM
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A/C shutting off before set temperature reached

My A/C unit shuts off before it reaches the temperature set on thermostat. When it shuts off, if I remove thermostat and short power to thermostat or compressor contacts, neither will not come on. So, I donít think it is thermostat.
The unit can run quite awhile Ė like an hour before it shuts off. Then, at some point Ė say 15-30 mins, it comes back on. I donít think the there are any settings you can set on unit itself that I have read about in other threads. Any suggestions on what to check?
 
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Old 07-06-17, 09:46 AM
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When was the last maintenance done? Check your filters. This can happen if the air handler coil freezes and triggers a freeze sensor. Also could be drain pan not emptying fast enough so needs cleaned.
 
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Old 07-06-17, 09:50 AM
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Are there any safety shut offs on that unit?
 
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Old 07-06-17, 10:47 AM
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I have not had a technician out to do maintenance for couple years. Replaced filter. Checked drain pan shut-off switch - working fine. Cleaned drain line. Air handler and outside coils are clean. Only safety shut-off I am aware of is on drain line. How do I know/check if air handler coil freezes? What is cause/solution if it is?
 
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Old 07-06-17, 10:59 AM
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What is the make & model of the unit? I would contact the manufacturer.
 
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Old 07-06-17, 02:56 PM
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I should have asked: When it shuts off do both the indoor blower and outdoor compressor stop?

Freezing would be low airflow or low pressure. Some outside units have a sensor to shut down if refrigerant pressure is too low. Usually the indoor blower still runs when it happens. It sounds like you've got the maintenance issues covered and I'm out of easy diy ideas so you need to get a technician out to review the system.
 
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Old 07-06-17, 06:44 PM
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If we are talking about central air, there should be a sight glass. If you see bubbles, the freeon is low.
 
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Old 07-06-17, 06:50 PM
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Welcome to the forums.

There is not always a sight glass.

When the system fails you need to determine if it's the inside blower, the outside condensor or both. Typically a condensor fan problem will cause the unit to run a short while and then shutdown. In that case the inside blower will still be running but the air will be warm/hot.
 
 

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