Rooftop AC fan barely moving

[inverseParanoid]

Edit: the fan also makes a noticeable and constant humming sound when it's running

Our last renters ended up having a problem with the rooftop fan

"we seem to have lost all power in the ac over night. It turns on, and I'm pretty sure the condenser is kicking in, it seems to be cold, but there is no powered behind the fan...
Any thoughts?"
(An hour later, before I responded he added...)
"I think we're good. Turned unit off for a while, and a lot of water drained off the roof. I think it was at least partially froze up. Lots of air flow now."

I thought the problem was fixed but then this weekend when we took it out for the first time since then and I turned on the fan and it was barely moving it all. The weird thing is that when I turn the fan on high it moves faster but is still incredibly slow (slow enough that neither speed causes any noticeable air flow whatsoever).

I'm up on the roof right now and both the fan that draws air from the AC block and the fan that blows air into RV cabin run at that same slow speed.

I've tried manually moving the fan blades and they seem to move fine. I even tried spinning them a little and then switching the unit on (but I haven't tried turning the unit on and then "jumpstarting" the fan because I'm a little scare of damaging something).

The renters said that whatever happened it ended up tripping one of the circuit breakers. I checked all the circuit breakers and the fuses next to them and everything looked fine. They also said that the problem occurred after running the AC for like 16 hours straight at a high level.

I opened up the service area from the roof and snapped a couple of pics in case that helps. https://imgur.com/a/krcnY

[navegator]

Las February 2016 we had to replace the Coleman unit that was installed in June of 20014, the Dometic that was original lasted 14 years, replace the junk from Coleman with a Dometic.

navegator

[j-d]

Or, from your problem statement, seems you could replace only the fan motor and install a new capacitor, about $125 total. Amazon has the motors.FASCO Motor for Coleman

[inverseParanoid]

The roof cover says Coleman Mach. I typed the model number into google and this came up as its replacement. http://www.rvproductsshop.com/coleman-mach-3-plus-13-500-btu-air-conditioner-48203c966.html

[j-d]

RV air conditioner (and it always helps to know make and model) doesn't use a Start Cap on the Fan. The value of the Fan Run Cap will be the lower of the two. Say 5-10 mfd for Fan and 35-40 for Compressor. Compressor may/may not have a Start Cap in addition to Run, but will always have Run.

A new or known good Fan Cap sounds like a pretty safe bet to begin your troubleshooting. If it wasn't running up to speed, it could also cause the evaporator core to freeze up.

[inverseParanoid]

After reassembling everything and getting down from the roof and plugging back I. I decided to turn it on and "jumpstart" it while it was on. It didn't jump start on low, but then I turned it up to high and gave it a spin it started right up. Now it works on high and low. I'm wondering if maybe the start capacitor is going bad and that's why it needed a jump start? I turned it off and turned it back on and it worked fine. I'll try turning it off for the night and then try it again tomorrow afternoon to see if it needs a jumpstart or not.

[Dusty_R]

Check the voltage at the unit when running.