My Dometic duo therm unit sounds like it runs when the power is off but no air comes out of the vents

The braker is getting weak and needs to be replaced the act should be cleaned as the coils get dirty and make the units work harder

relay module.

What size & type generator? On start up the AC unit can draw as much as 17-18 amps in some cases, and if your generator is not designed for a quick draw like that it will die.

Sounds like a reversing valve solenoid.

You will need at least a 5000 watt generator to run that and a few lights etc... for the camper.

heatman101

Hi, Sounds like your fan motor has gone bad...
Here is a tip about trouble shooting your air conditioner...

Air Conditioner Trouble -Review the Possibilities
http://www.fixya.com/support/r3571569-air_conditioner_trouble_review_the_possi

heatman101

I had the sam problem, took the thermostat cover off and tightend and refastend the wires, so far so god

What happens when started in just fan mode? Sounds like relay stuck.

Sounds like the ducting have come apart in some areas or blocked in some way. Take the supply grills off and with a shop vacuum try and reach as far as you can.

Your compressor is trying to restart after it shuts off which is causing a power draw down changing the sound of the fan speed change. Check voltage power supply and insure that the power supply cord is heavy enough to carry the necessary load.