Same thing happened to me several years ago, and I agree with Caveman's post above. I had to climb up on the roof every time to take off the cover, oil the shaft, and turn it by hand several times to get the air conditioner fan motor to run after the trailer had been stored for several weeks. After oiling the motor it would run fine until the next storage period and then repeat above.
I solved the problem by junking the 13 year old unit and replacing it with an
Atwood Air Command 15,000btu unit. This has been on our roof for two years now and functions perfectly plus it has heat which our old Dometic unit did not. We are perfectly satisfied with the change and hope it outlasts us! :B
Barney