Roof Air Conditioner Troubleshoot

by Cathy
(Arizona)

I have a 2007 motorhome with a Duotherm Roof Air Conditioner that is now making a high pitched sound when running. What is it and what needs to be done to alleviate that?

Comments for
Roof Air Conditioner Troubleshoot

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Apr 10, 2011

Roof Aair
by: Anonymous

Thanks for the tips: I bought a new AC unit. Fixed that problem in a hurry!

Jul 14, 2010

One Step At A Time
by: Wil

High-pitched sounds in machinery usually means metal-to-metal contact without benefit of (sufficient) lubricant. In your air conditioner, this can only be the motor which drives the compressor and the fan/blower. First, turn off the breaker switch that controls the Air Conditioner (A/C). From down below, remove the four screws holding the lower shroud after pulling the knobs off and set it aside on the couch or table. Now, using a step-stool and flashlight, look around and identify the major components. Any leaves or other debris poking in from the outside contacting the fan? Give everything a good dusting while it's opened up. Nothing in the way of the blower? Close it up and replace the shroud. Don't forget the knobs. They only fit one way.

That was the easy part. Give it a test-run. Still have a bad noise? Now you must decide if you are able and willing to climb onto the roof for further troubleshooting. If not, take it to a qualified Duo-therm dealer (listed in your owners manual and probably on their website).

If so, making sure you have again turned off the breaker, grab wasp spray, a regular and Philips screwdriver, a pair of pump pliers (suitably sized ViceGrips will substitute) and an adjustable wrench, if you have one, otherwise bring along a 7/8" and 1/2" open-end wrenches. Look carefully at the exterior of the housing - any wasp nests? Hit them hard and fast, then retreat until 30 minutes or so have passed. You'll know when it is safe - wasps still flying around, checking their nest? More iced tea and the soaps. All clear, remove the four (usually) nuts and washers holding the shroud on and carefully lift the shroud up and off the AC unit. All clear? Clean all debris, leaves, twigs, spider nests, Geckos, and other creepy-crawlies who have been hanging out, using your A/C as their home. Examine, dust and clean, and straighten any bent fins in the condenser coils. There may be an additional, interior shroud for the blower fan. First, visually inspect for debris that may be causing the noise. Then, remove the screws holding the fan shroud. Have wasp spray handy, just in case (not usually an issue this deep into the A/C but one must allow for these determined critters at every stage). With the shroud off, turn the fan shaft. Feel any significant resistance or scraping? Nope? Got me... probably a compressor and not something readily repairable by you. But, if you feel scraping or drag or rubbing, then examine the bearings and see if they are replaceable in the field -- if so, get the numbers off the unit and call a dealer or supplier of choice and order the parts. In the meantime, give the bearing a shot of WD-40 and rotate by hand. Less noise and resistance? Great = lube it up, close it up and wait for the parts to arrive. If no ... you probably need to prepare yourself for a complete replacement = big buck$. Take it to a dealer you trust and get a second opinion, of course.

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