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KP616 08-06-2012 11:08 PM

Condensor fan shuts off after exaclty 10 miutes
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Hello to all,

I'm extremely frustrated and looking for any help or suggestions. Although my problem seems fairly common, I have yet to find a solutions in any of the other forum posts.

I have a Rheem AC unit that shut off in the middle of the night a few days ago. The next morning, it was pretty warm in the house but I could still hear the air handler running in the attic. I go outside and discover that the unit is not running. I go to the breaker panel on the side of the house and find that the AC breaker has been tripped. I reset the breaker and turn the unit back on. The compressor kicks on but the fan motor does not. I was able to nudge the blade with a long screw driver enough to get some momentum going and then the fan motor would work for a little while.

I assumed the fan motor was bad so I went to Grainger and they matched it up with a new one. Went home and cleaned the coils and the housing and replaced the fan motor. Unit ran fine for about 10 min and then the fan shut off.

The contactor was a little dirty looking so I went and picked up a new one of those too and replaced that. Same thing happens, fan motor shuts off after 10 min.

I went back to Grainger and matched up my old capacitor with a new one and replaced that as well.

Now I have a new motor, new contactor, and new capacitor...and still the same problem, the fan motor shuts off at 10 minutes. I can turn the thermostat to off and wait a few minutes, then turn it back on and the unit will fire up fine for 10 minutes and the fan motor will shut off again. The compressor continues to run every time but I quickly shut off the unit to prevent the compressor from over heating (which I assume is why the breaker was tripped the first time when this happened in the middle of the night).

I've verified that the ratings for all new parts match the old parts. I find it very strange that the fan motor has continued to act the exact same way from the beginning and through each addition of a new replacement part.

Just out of curiosity, I wired back up the old fan motor with the new contactor and capacitor and the same thing continues to happen.

Could there be a short somewhere caused by the original over heating that tripped the breaker? As I mentioned, the breaker was only tripped that first time.

I've attached a PDF file of the wiring diagram I made in Photoshop of how my unit is wired. I've tried this wiring with and without the Brown/White striped wire from the fan motor, same thing happens both ways. If anyone sees any mistakes, please let me know.

Thanks in advance for any suggestions or tips!

Doc Holliday 08-06-2012 11:28 PM

Condenser fan wire should never touch herm of a capacitor. That black from the condenser fan motor needs to go to the same black output side of the contactor, line 1.

Then the yellow common from the fan needs to go to the other side of the contactor.

scottmcd9999 08-07-2012 06:00 AM

Also, in the future remember that you should ALWAYS replace the capacitor when installing a new motor.

Note too that the Yellow wire and the Brown/White wire are the same - you don't need to hook up that Brown/White wire if you stay with the dual capacitor, although I suppose it wouldn't hurt anything.

KP616 08-07-2012 10:03 AM

Wow! Thanks Doc Holiday and Scottmcd9999...unit has been running all morning after the wiring change. I'm still scratching my head on this one though because this is not how the wiring was configured before. I took photos of the wiring prior to disconnecting anything, which was only the 3 fan motor wires on the first go round. Also, I had a AC tech also said that the black fan motor wire shouldn't be connected to the capacitor but instead to terminal 1 of the contactor as you suggested... but he said that was the only wiring mistake. So when I told him that I made that 1 wiring change and the fan motor now was getting no power, he was stumped (he was also looking at the wiring diagram I made)! Also, the original wiring diagram sticker on the inside of the unit door shows the yellow or orange fan motor wire (common wire) going to the common terminal on the capacitor...strange.

Thank you again Doc Holiday and Scottmcd999! I've spent the last few days beating my head against the wall in my 89 degree house, and you solved my problem in a few minutes!

scottmcd9999 08-07-2012 10:27 AM

Yellow/orange on the ORIGINAL motor may have gone to C on the cap (in fact that's fairly normal), but I can guarantee you that the Blk wire from the fan motor did NOT go to the Herm terminal on the capacitor. The fan never would have worked correctly in that configuration, at least not for very long.

Confusion often sets in when moving from a 3 wire to a 4 wire. If you just remember that the Brown/White wire is the same as the White (or yellow) wire internally (and you therefore don't need to use Brown/White) then it makes more sense.

Doc Holliday 08-07-2012 10:39 AM

You're welcome.

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