A/C condensor fan not turning

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  #1  
Old 07-02-09, 07:32 PM
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A/C condensor fan not turning

I probably should have waited until tomorrow to post this after I have a chance to check the system out thoroughly in the daylight. However, I am anxious to see where I should start looking for the problem. This afternoon I heard a loud pop outside at back of my house where condensor unit is located. Being close to the 4th of July, I thought it could have been someone trying to get a jump on the holiday festivities. However, after 2 or 3 hours I noticed that the A/C was not working, checked the breakers & all OK, went outside and found that the condensor fan was not turning. I also found that the top of the fan motor in center of unit was EXTREMELY HOT even though the entire unit is in the shade, and fan had not been turning for several hours. This is a Payne condensor installed with a Carrier (same difference) air handler in 1982, and the only problem I have had in the past 27 years was a bad capacitor that had to be replaced about 10 years ago. Does this sound like it could be the problem again, or a condensor fan motor that is burned out. How can I check? Multimeter? Need help fast due to the temps. here in NC. Thanks!
 
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Old 07-02-09, 08:14 PM
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Does the motor spin freely? Look inside the unit- see anything obvious like a burned wire terminal or the like? Do you have a multimeter? If yes, make a sketch of where the fan motor wires go, remove the wires and ohms test the fan motor [let it cool off for a while first]. The readings will be low but you should get a reading among all the wires.

Example:

the motor has 3 wires, black, purple, brown. Test black to purple, black to brown, purple to brown- there should be a resistance [low] between each pair. if not the motor has an open winding. Also test each wire to a cleanly scratched place on the motor casing [scratch a spot with a screwdriver], you should not get a reading, if you do, the motor is grounded. If the motor tests ok, try replacing the capacitor.
 
  #3  
Old 07-02-09, 10:58 PM
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Thanks for the prompt response- I'll give it a go first thing in the a.m. & let you know whassup.
 
  #4  
Old 07-04-09, 11:11 AM
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Well daddyjohn, this one turned out to be a simple (so far) problem. I took panel off back of compressor & found the capacitor had exploded (the loud pop I heard). The top was blown off , strips of metal and oil inside capacitor blown all over inside of control box. It was yesterday, July 3rd, and you guessed it...Murphy's Law:
Your A/C will go out during July 4th holiday when every store/supplier is closed (this is same law as oven going down on Thanksgiving Day, or furnace going down the last week of the year).
I will have to "sweat it out" until Monday for local HVAC supplier to open.
Two ?'s though- Do I have to worry about PCB in a capacitor that is about 10 years old? What caused problem in first place?
 
  #5  
Old 07-04-09, 11:51 AM
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Well..DJ isn't around right now..but to answer your ?'s best I can...no, don't worry about PCB's, wipe it all down with paper towels and some cleaner.

Caps get old..they don't normally go like yours did, but it can happen. If it works, its a cheap fix..but if it doesn't..you may have other problems.

Since you have time, you'll probably get some other replies if you feel like testing for a grounded compressor or similar.
 
  #6  
Old 07-04-09, 04:33 PM
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Yes, before installing a new cap, test the compressor motor. Scratch a clean place on the larger tube at the compressor, take the wires off the terminals [take pic or make a sketch of where they go], ohms test each pin to ground [the clean spot on the tube]. There should be no reading. Then rest pin to pin. You should get a resistance reading but very low [don't be surprised if you get single digit readings], if you get 0 resistance on any 2 pins, that motor winding is shorted. You'll need to use a digital meter for this test.
 
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