A/C only works when its cool outside

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Old 07-19-10, 02:10 PM
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A/C only works when its cool outside

I have two units - one for basement and another for upstairs that sits in the attic. The one in the basement works fine when its hot outside. The upstairs one just stops when it gets hot outside. Works great when it cools down in the evening and throughout the night. Any suggestions on how to fix this would be most welcomed on these super hot days of summer. Thx!!
 
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Old 07-19-10, 04:03 PM
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Could be something as simple as a loose blower door or a return duct come undone
 
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Old 07-20-10, 02:22 AM
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if the condenser outside isn't running with the sun on it.... it might just need a good washing from the inside out.can't be short of freon because you said it runs fine at night.if you can catch it running in the day grab the thin copper line just out of the condenser if the unit starts and that line gets super hot the condenser is fouled with dust dirt yard stuff.check the same line on the other system running in the day you will feel a warm line as it should be.to clean shut power out there cover compressor with garbage bag..spray noozle garden hose from the inside out.DON"T blast it easy does it.you might reach in to see coil but you can remove the top of the unit and tilt off to the side
 
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Old 07-20-10, 07:41 AM
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Arrow Also, Check for Return-Air leaks from the attic...

Good advice sminker. Cut all the power to the outside unit & also to the furnace or air handler to protect low voltage power.

The condenser could be shutting down on the high pressure switch.

If the Return-Air is drawing in hot air from the attic that could also overload the condenser. Check for Return-Air leaks.
 

Last edited by HVAC RETIRED; 07-20-10 at 07:44 AM. Reason: Cut all power...
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Old 07-20-10, 03:27 PM
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Both outside condenser fans seems to be running when the sun is on them. Both of the condensers outside are blowing hot air. There is condensation on the copper wire from one of them (the larger one and I am assuming that is the basement and first floor) and the copper wire of the other condenser (small one) is dry and normal to the touch (not hot). Do you think it still needs a cleaning? If so I will turn off the circuit breaker for the house and clean it out the way you suggested. Please let me know. Thx
 
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Old 07-20-10, 03:35 PM
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One more thing - although there is no humidity in the basement there is a lot in the first and second floors of the house. Again the basement is real cold, the first floor so-so and the upstairs not at all.
 
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