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Bratton

Condenser fan motor and capacitor

7 posts in this topic

Ok guys. a real do it yourself mistake.  My 8 year old condenser fan motor stopped working. might have been just the capacitor but decided since the motor was old AND had an AC repairman tell me (5 years ago) that the motor was failing I just decided to put in a new motor and capacitor. No problem, fired right up only problem was I had the fan blades on upside down. realized this right away and turned the blades around. BUT! Apparently I did not tighten down the set screw on the shaft! The blade reversed threaded itself up the shaft till the blades hit motor housing and stopped turning. Did I burn the motor out? Maybe fried the capacitor? More serious damage? Help me out guys. Thanks Bratton.

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Hi Bratton, chances are you didn't hurt the motor or cap if you caught it right away. But you should change the fan blade now. When it came in contact with the motor housing, I'm sure it tweeked it. And you can't straighten them back to factory spec. Good news is they are fairly inexpensive. Make sure you order the correct rotation (CW or CCW), pitch (in degrees), blade # (3 or 4), and shaft bore size (most likely 1/2"). Your old fan blade may still have the sticker on it with the part number and above info on it. If not, take it to a local HVAC parts store and they can help you there.

When installing new fan blade, use BLUE Loctite and snug it down real good. And get proper distance on the shaft for the new blade. Use your old motor and set it to that on the new one.

As far as the motor and cap go, you can test them once everything is reassembled. With the power disconnect removed (no power to unit), there should be absolutely no slop or grinding (bearing issue) and very little resistance when manually turning the blade. Electrically the best way to check it is with a clamp-on ammeter. Check the manufacturer's sticker on the new motor. You are looking for the FLA (full load amps) rating. With motor running, check the black fan wire off the top of the contactor or the pcb. It should be less (maybe up to half an amp) than the FLA.

The cap can be checked with a DVOM with capacitance function. Remove power disconnect. Remove wires from cap with needle nose pliers. Short cap contacts for 5 seconds. Use an insulated handled screwdriver. Read across cap contacts. Check micro-farad uf rating printed on new cap. If outside the plus or minus percentage limit, change it. Be careful, caps hold a charge, even with power removed. It is crucial that you discharge the cap before handling and testing.

Parts can be found using the search box right here on appliantology.org with part name and/or part number. 365 day no hassle return policy, even electrical parts. We'd appreciate it.

Edited by beam current

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Thank you Sohei. I did not mention in my original post that I did reset the blade but the motor is not coming on. When you turn the AC on the contact switch engages but does not seem to be any power from the capacitor to the motor. not even a humming sound like it is trying to turn. I am ordering a new fan blade but isn't going to do much good if the motor won't come on. Thats why I was thinking capacitor.

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Hi Bratton, Ok, do you have access to a DVOM? Sears, Harbor Freight, neighbor? You really need one to read for 240vac across the top and bottom of the contactor.

Does the compressor turn on? You'll hear it. Do NOT let it run for more than a few seconds at a time to test without the fan. Or is it just the fan that does not?

Senerio #1: The circuit breaker is tripped for the outside condenser unit. It will be a dual-ganged 30 or 40 amp breaker. There is also a separate breaker for the air handler. We are not concerned about the air handler breaker. Cycle breaker off to on whether it looks fine or not. There may also be in-line fuses in the power disconnect box mounted by the condenser unit. Cycle breaker off and check the disconnect. Resistance check with the DVOM. All fuses should be less than half an ohm.

When there is a call for cool from the tstat, that is a 24vac signal to each side of the contactor. It will engage the high voltage plunger, but if you don't have 240vac to bottom of the contactor, the compressor and fan motor will not come on.

This is why a DVOM will tell you exactly what is going on.

Scenerio #2: New fan motor is now jacked. See my first post on how to check with DVOM/ammeter. No hum leads me to scenerio #1.

Scenerio #3: Capacitor is jacked. Does the fan have its own dedicated capacitor or is it a dual run cap, shared with the compressor? 2 sets of contacts or 3? If it is a dual run cap, you will see "fan, herm, and c" embedded into the top by each set of contacts. Is it bulged or deformed in any way? Again, see my first post on how to test. This would be the cheapest to change, but using a DVOM will tell you exactly what is wrong.

Scenerio #4: Contactor has failed. Least likely though. You can visually inspect the contacts for severe pitting and black carbon deposits. Use a very bright flashlight.

Be aware you are working around extremely dangerous high voltage and high current equipment here. If you are not comfortable and knowledgeable with working around these hazards, you may want to consider calling in a professional.

Good luck and let us know what you find please.

Edited by beam current

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After asking alot of questions from anyone who would listen, I was told it sounded like a blown fuse or the circuit breaker had tripped. Didn't even know there was 2 fuses behind a plastic cover in the power disconnect  box. My neighbor came over with a tool and poked around and said there was no power. I cycled the breaker and tried again, still nothing. Neighbor tested the fuses and one was shot. Went and bought 2 new fuses and replaced them. Success! Fired right up and running great! Thanks for all your information, very helpful. Again all of this would have been unnecessary if I had just tightened the set screw on the blade. Looks like the fuses did the job they are made to do.                                          

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Good job Bratton. Glad to see scenerio #1 was the problem and the least expensive fix.

I highly recommend still replacing the fan blade. If it runs with an out of balance blade for long, it will destroy the new fan motor bearings fairly quickly.

Enjoy the cool air.

Edited by beam current

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Thanks again for the help Beam. Got the motor and capacitor thru this site. Repair Clinic I believe it was?

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