A/C compressor fan not starting


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Old 06-26-14, 10:06 AM
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A/C compressor fan not starting

My A/C compressor fan does not start when a/c kicks on. The fan motor was making some noise and when I hit the top of the unit blade rotated a revolution, hit it again and it started running, I equate this to passing the stick start test. System cools when running. Not sure but the fan may stop in the middle of cooling but may only stop when a/c goes off and comes back on. A/C company cant make it out for a few days and it seems like its the capacitor and I'm comfortable replacing that. just want conformation on whether the start cap needs to be replaced or the run cap. I believe the run cap is the large cylinder one with "50uf 6uf 440vac" on the side and three terminals, and the start cap is the oval cylinder with 2 terminals. Thanks for any input you guys can give.
 
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Old 06-26-14, 10:43 AM
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You're correct, the Start capacitor is the one that needs to be replaced. However, I can't tell you which one is which. If there is a wiring diagram inside the outside unit, it may show wire colors which may help you determine which is which.
 
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Old 06-26-14, 11:36 AM
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Welcome to the forums.

A make and model of the compressor unit would be helpful.
 
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Old 06-26-14, 12:27 PM
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The dual run cap requires replacement.
The start cap does not control the fan motor.
 
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Old 06-26-14, 03:40 PM
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Considering the price of caps, I would replace both, if doing it myself.
 
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Old 06-27-14, 06:44 PM
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Update

So I purchased a 50mF/5mF 440 dual run cap to replace. Was confused when trying to install as the wiring diagram didn't match; no fan wire (purple) and 2 common (red). Upon further investigation the 2nd common (red) was jumping to another 5mF cap with my fan wire (purple) coming off. It seems this is a common way to fix cap issues to only replace the low cap for the fan motor? So I took out both caps and hooked up my new dual run cap connecting all three wires (F,C,H) according to wiring diagram. So far, so good. Just want a heads up if this sounds right to you guys.
 
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Old 06-27-14, 06:50 PM
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Many service guys just carry single capacitors and will just install what's actually needed.
I've always been a big fan of separate capacitors.

What you did sounds fine. If it works ok then you're all set.
 
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Old 06-27-14, 07:44 PM
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If I don't have a dual cap in the van but I can do the job with 2 caps and save the customer a trip charge for the parts house I install 2 caps instead of a dual cap. It does seem like separate caps swell up less often but they don't fit as well in many electrical compartments.

If a 45/5 x 440 dual cap reads 0 and 5, I can't install just a 45uF cap. I would worry that the other half will soon fail.
 
 

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