Hi,

My AC unit (Rheem 10AJB36A01) stopped working a few days ago. Temperatures here have been in the 90s. The AC tech looked at it and said the capacitor was bad, replaced the capacitor and it started right up.

However, a day or two later the fan stopped working again. I turned the AC off, waited overnight and turned the AC back on, and the fan started working fine, but after a couple of hours, again, the fan stops working, there is a loud noise from the AC, and I turn it back off. On hot days it stays running for about an hour before stopping again. It seems that the motor is overheating and stops running, but this is just a guess. The grill right above the fan motor is very hot to the touch when it stops running. It ran fine all night but when it got hotter outside it stopped again.

Now - to the question (sorry for the long preamble):

The label on the fan motor says that it requires a 3 MFD capacitor, however the tech put in a 45/5 MFD capacitor (voltage is ok at 370). Could the difference between the 3 MFD and the 5 MFD that's there be causing the fan motor to overheat? Or do I just need a new fan motor?

 

you need a new fan motor............................

 

Thanks.

If I get the exact same motor, do I need to worry about getting a 3 MFD capacitor (45/3) or is it ok to leave the existing 5 MFD capacitor in there (45/5)?

 

If it were me, I would put the correct one in if you are going to be in there anyway.

 

The new motor should list the required capacitor needed. It would be best to use what is specified.

 

May not need a new motor!

Blower motors require decent temperature air circulating over them to keep them from over heating!

Could be drawing hot air from the attic into the Return air; very important to check air temp just before the motor.

May not have enough air circulating over the motor.

Is the motor clean?

Last thing; motor could be bad or wrong MFD capacitor rating.

 

It has actually gotten worse. At first I could turn the AC on and have it run an hour or so (all night when it was slightly cool) before the fan would stop. Now (a day after it ran all night) the fan doesn't even start even after it being off for hours. I tried to help the blades along with a stick but they did not move freely and even when they moved a little bit, the would immediately stop.

So at this point it seems that the original diagnosis was correct and I need a new motor. I'm planning to get the motor with the part number that replaces mine, and it also says "3 MFD", so I'm thinking I should replace the "45/5" capacitor with a "45/3"?