Condenser fan hums but won't turn

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  #1  
Old 09-24-12, 06:44 PM
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Condenser fan hums but won't turn

This condenser is a Lennox AC13-042-230-02. The unit is about 6 years old. While the compressor carries a 10 yr. warranty, the rest of the condenser is out of warranty.

The condenser fan hums even when the thermostat is set high. When you set the thermostat low, the compressor turns on but the condenser fan still will not run.

Another post mentions a similar problem. His problem turned out to be a faulty capacitor. This dual capacitor, however, actually comes close to spec. It measures 53.5/10.1, which is close to the spec of 56/10.

When the thermostat is set to high temperature, you can read 10VAC across the load terminals of the contactor (relay). When the thermostat is set low, you read 230VAC across those terminals of the contactor. Manual turning of the condenser fan (with power off, of course) results in a faint scraping noise once every turn. The condenser does not have the optional timed-off control.

This question is primarily about the humming noise. If the contactor is not energized, why is the condenser fan humming?

The manual is here:
http://0190acd.netsolhost.com/manuals/AC13_Series.pdf
Thank you in advance for your thoughts!
 

Last edited by 5tudent; 09-24-12 at 07:15 PM. Reason: clarification
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  #2  
Old 09-24-12, 07:23 PM
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The Motor has failed and is grounded.
 
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Old 09-24-12, 07:45 PM
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Thanks

Thanks for the rapid reply, theapprentice, and thank you for shedding light on the problem! If the motor can ground like this, why doesn't Lennox use a relay that switches two legs to prevent this danger?
 
  #4  
Old 09-24-12, 08:49 PM
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They are probably just trying to save a buck. I've never seen any danger as a result of it. Its 240 volts, you have to know what your doing or it can always be dangerous.
 
  #5  
Old 09-25-12, 06:33 AM
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Doesn't sound like its grounded to me. Sounds like u have a bad spot on motor or bearings are going bad. Does motor have oil ports? If so put a lil zoom spout oil in ports. Put a lil oil around shaft seal.
 
  #6  
Old 09-25-12, 06:36 AM
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Actually just realized I missed a whole section of this forum. Does sound like a short. My apologies!
 
  #7  
Old 09-25-12, 05:17 PM
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I have never heard of a dual run capacitor with a rating of 56/10! maybe 55/10 or 55/7.5
How did you check the capacitor specifically? Can you post a picture of the capacitor? Regardless if you replace the motor you MUST replace the capacitor as well.
 
  #8  
Old 09-28-12, 06:16 PM
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You're right, hvactechfw. I checked the capacitor nameplate and also checked it using a Fluke multimeter. A Lennox parts dealer said that the installing dealer probably replaced the capacitor previously. (It's tough to find a reputable dealer here.) They also said that some higher microfarad values can be used without a problem, but lower capacitances would cause trouble. You would know whether they are correct.

The new motor arrived from CozyParts today. It is an Interlink YSLB-250-6-B007-XXXX (aka Lennox 68J24). Unfortunately, the new 10W36 capacitor did not arrive yet.

Is it alright to run the new condenser fan motor with the 56/10 capacitor until the new 55/7.5 capacitor arrives after the weekend? Thanks for your advice!
 

Last edited by 5tudent; 09-28-12 at 06:46 PM.
  #9  
Old 09-28-12, 06:31 PM
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hvactechfw, I'll take the old capacitor out and photograph it for you soon.
 

Last edited by 5tudent; 09-28-12 at 06:56 PM. Reason: adding information
  #10  
Old 09-28-12, 08:35 PM
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no, it is not ok to use it with the old capacitor. You can go higher in voltage but not capacitance on capacitors.
 
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