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Old 06-12-2010, 04:50 PM   #1
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Love this site Hi Gurus, Been trying to fix my unemployed son's AC-fixed one problem by replacing the dual rated capacitor (original was 3/30/370, new one is 30/5/370, but newer one is physically smaller). The problem now is the fan shuts off after 10-15 minutes. Suggestions from this site said clean the coil (looks like radiator fins?)-which I did-was very dirty/caked with grass, and check the motor bearings which seemed OK but I WD40'ed it anyhow. I'm thinking the different microfarad rating is OK since it's a higher rating. I see the contactor deenergize after the fan shuts off. Not an HVAC guy. Need the experts' suggestions.

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Old 06-12-2010, 05:07 PM   #2
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The 30 is for the compressor and the 3 which you NEED is for the fan motor. Using a 5 will overheat the motor. Probably the motor is worn and damaged from having to work hard against the dirty condensor coil and they do wear out from age anyway. WD 40 is more of a solvent/kerosene based and sleeve bearings don't like oil anyway.

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Old 06-12-2010, 05:10 PM   #3
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WD40 is one of the worse things you can use to lubricate a motors bearings.

That cap is not good as a permanent replacement. Need to get the proper one(bigger is not always better.

Is the fan shutting off, and shortly after that, the contactor opens? id so, good chance its the cap. or, the motor is what took out the old cap. And you need a new motor and another new cap.

Does the condenser have pressure controls on it.
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Old 06-12-2010, 06:45 PM   #4
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Can you give me more info what and where to look for condenser pressure controls?
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Old 06-12-2010, 07:06 PM   #5
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They would be tapped into the copper lines, and have wires running to them.
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Old 06-13-2010, 12:36 PM   #6
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Didn't see condenser pressure controls but wired in a 3 mfd universal mini in place of the 5 leg of the 30/5. Fan ran longer after that but still shut down. Didn't see pressure control wiring. Are there places that will test the motor to be sure it's bad? Thanks guys-you're a big help!
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Old 06-13-2010, 12:55 PM   #7
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The motor costs less than $100 and a motor shop usually is too expensive to test fractional hp motors. As it heats up under load the bearings seize and they cannot test that anyway. Put your hand on the motor when it stops and see if it is blazing hot. You can also checks its amperage after it has run for some time and read it off the motor or unit rating plate. If you decide to replace it be careful how you pull the blade off and note the position up/down of the blade vs the cowling. I would take a pic with a camera first. Too high or low affects the airflow and can be a problem.
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Old 06-13-2010, 01:23 PM   #8
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Thanks Yuri---gettin too deep for me, think I'll have to call out the pro's.

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