Rear AC FAN Hums no start.

Remove ceiling grill.......you can then see/touch squirrel cage.
See if it will rotate by hand. If it does then turn on A/C and see it it works.

Our Biscuit friend has it, the shafts like to rust and seize up. If that's what happened then use something like vice grips to force the shaft to spin from above. Lube the bushing up and turn the fan on. I have to do this to mine every spring.
Also, if you try to make it start too many times when it's seized the hard start cap will puke.

Hi,

I had to give my ac fan a push every spring for years and years.

Old-Biscuit wrote:
Remove ceiling grill.......you can then see/touch squirrel cage.
See if it will rotate by hand. If it does then turn on A/C and see it it works.

AC on mother-in-law's camper did that; hum, no spin, would run once you spun the squirrel cage fan by hand.

Problem in her case was the capacitor which are common failure point on Rv and residential ACs.

No need to get replacement from an RV shop. Take the old one to any shop that works on electric motors and they can match the specs printed.

A bad capacitor is easy to spot as it will be swelled up and possibly split & oozing black goo.

I think there are two caps in there and the problem is usually a 'start capacitor' that goes bad if the squirrel cage is free. A lot of the time they will expand in size when they go bad so maybe it will be easy to identify. They are cheap enough so you can replace both of them while you're up there,,, if that's what it is.

I agree on the cap,,I had a f'ver do the same thing several years ago and my coach air did same thing this aummer.

Thanks. I'll try to spin the fan from the inside tomorrow.
I have had caps go bad before but it was always the compressor cap.
We use the RV almost every other weekend so I will be surprised if the fan is froze up.

Will report back.

Big Katuna wrote:
Thanks. I'll try to spin the fan from the inside tomorrow.
I have had caps go bad before but it was always the compressor cap.
We use the RV almost every other weekend so I will be surprised if the fan is froze up.

Will report back.

Both my fan and compressor (Dometic units) have and share a run capacitor as well.

Check for a wasp nest in and around the fan under the shroud outside.

So I pulled the inside covers off. I should have said I have Coleman ACs
You can not see a fan from the bottom so it looks like its time to go up on the roof.