A/C Fan keeps running - Wont turn off


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Old 05-22-08, 05:40 PM
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A/C Fan keeps running - Wont turn off

My ac fan keeps running. I got the ac on at the moment. It will cool to the temperature set and shut off but the fan outside runs all day long! How do I fix it? My last electric bill was
$500!!! When it was working right it was just $200!! =( Also my fan is on AUTO. I do not have it on ON so it shouldnt be running constantly.
 

Last edited by charmedpixie; 05-22-08 at 07:47 PM.
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Old 05-22-08, 10:02 PM
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Wink

It will cool to the temperature set and shut off but the fan outside runs all day long! How do I fix it?
Ill bet the compressor also stays on then. Can be 24V wires have a short to unit???? Contactor in outside unit stuck on????? with burnt points. If so get a new one
 
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Old 05-22-08, 10:11 PM
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I don't know home a/c, but automotive a/c usualy has a high pressure switch that controls the fan and it wasn't uncommon for the switch to short out. Might be worth a look?
 
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Old 05-23-08, 08:16 AM
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hey guys thanks for the help but .... where do I look for this short ? lol.
 
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Old 05-23-08, 08:44 AM
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Check to see if the outside unit is running even when the thermostat is in the OFF position. This would indicate a bad contactor (relay) outside or something bad to it's control.

This situation is very bad for your compressor,eg running without the indoor fan on. You could have a compressor failure at any moment. I'd shut it off and call for service immediately from someone trained on your type of unit. $300 a month and potential compressor failure makes this call a no brainer.

These days, many outside units have electronics that actually control the compressor using the thermostat wires as inputs. This makes it necessary to follow your specific wiring diagram to diagnosis properly.

Important: The outside unit has 240 VAC at high amps usually unprotected by insulation other than a sheet metal cover. Normally a service person would start checking the control wiring with the 240 power off at the circuit breaker. However some systems require the power on for even the basic 24 vac testing.

If it's a simple, no electronics outside unit, a qualified person would start by measuring the Y wire at the outside unit compared to the 24 v common. If it is on (nominally 24vac) when the thermostat says it should be off (and the indoor unit fan is off), then something is wrong inside. But most likely, the Y wire will be off, meaning something like the outside contractor is failed in the on position. Usually they fail in the off position, so other issues like electronics are more likely. A lightning strike or power surge could have welded the contacts shut or could have shorted other control circuits.

Do yourself a favor, shut it off and call somebody.
 
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Old 03-23-09, 03:31 PM
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Cool AC compressor shuts off; fan keeps running

My problem is similar but different. My AC compressor will turn on, but after running for a while it shuts off (I've checked, the compressor outside is not running), but the fan keeps running. I can go into the garage and hit the side of the unit hard and the fan will then cut off. Trying to turn it off at the thermostat does not work. If I'm not here, the fan will continue to run, which is not good for my electric bill. Aside from calling for repair, any suggestions?
 
 

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