Compressor fan doesn't always turn on.


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Old 07-10-14, 10:33 AM
J
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Compressor fan doesn't always turn on.

We went to bed with the a/c on the other night and woke up with warm air coming out of the vents (I have a Lennox HS29-030-1p). I went outside to check on things and the compressor fan was running, but the compressor was not. I checked the capacitor and found that it was bad. I picked up a new capacitor at Grainger, installed it, and everything seemed ok.

The next day, we again notice that the vents are blowing warm air. I check outside again, and this time the compressor fan is not running. There is a faint hum, but I can't pinpoint where it's coming from. I tried turning the fan blades with a stick, and they seemed to spin freely. I checked the new capacitor again just to make sure it didn't suddenly fail, and it was ok. I turned the thermostat off and back on and after the built-in delay, the air kicked on and the compressor fan is spinning again. This continues to happen intermittently.

Is my fan motor failing? What is the likelihood that a fan motor and capacitor would both stop working at the same time? The hum seems to be coming from near the bottom of the unit (not the fan area), but it isn't loud enough to be the compressor actually "compressing". Is the compressor smart enough to not kick on if the fan isn't spinning? Any ideas about what could be going on? Thanks.
 
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Old 07-10-14, 10:44 AM
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The only way the compressor knows that the fan is not running, when it gets to hot and shuts down. Sounds like the motor is failing.
 
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Old 07-10-14, 10:52 AM
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Have you pushed the contactor button and see if that help ?
 
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Old 07-10-14, 11:01 AM
J
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No, I didn't know about the contactor button (I just googled it). I pressed it and everything came on. I'll wait a bit and try it again a few more times to see if I can replicate the problem.
 
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Old 07-10-14, 11:39 AM
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Ok, I've pushed the contactor 7 times now (I started waiting 10 minutes between pushes, and decreased the wait time down to 1 minute between the last two pushes). The fan came on every time. Does that narrow down the problem, or just mean that the unit is waiting for me to not be looking at it?
 
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Old 07-10-14, 11:53 AM
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The contactor controls both the compressor and the fan, so if the compressor is running but the fan is not, that rules out the contactor as the source of the problem. Since it's an intermittent problem, you'll probably have to wait until the system acts up again (compressor running, fan not). If you can catch it when the problem occurs, I would try to feel if the compressor fan motor is hot. It could be that there is a shorted winding inside the fan motor, causing it to overheat. When it overheats, the thermal shutdown kicks in and turns off the motor. When the motor cools off, the thermal shutdown resets itself and it runs again until it overheats.
 
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Old 07-10-14, 03:08 PM
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If the contactor is good, then the problem has to be either the compresser or the condenser fan, If you can disconnect the wires to the compresser, you will know if the fan is good or not (without compresser in there, the fan should run nonstop).
 
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Old 07-10-14, 04:11 PM
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Yes, as long as your looking at it it will start every time! Had one yesterday, started every time for me.
 
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Old 07-10-14, 07:44 PM
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Post the color of the wires on C, on Herm and on Fan on your new capacitor.

 
 

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