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Old 05-25-2023, 09:12 AM   #1
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Join Date: Jul 2017
Location: Lake Mary
Posts: 29
M.O.C. #20145
Rear Dometic AC freezing up - problem and solution

Unit: 2018 Montana High Country 381TH
Rear Air Dometic 13.5 AC
Note: I live in Florida in the Orlando area

When setting up to leave for a trip to Destin Florida the Rear AC stopped working after running all day in the heat. It would not turn on when you lowered the temp on the thermostat. Got on roof and took the AC cover off, Styrofoam cover and plastic cover to see if anything was obviously wrong. Fan motor spun, no blockage of drain holes, no oily substance to show leaking Freon, no burnt wires. So all seemed OK with the unit itself. Drove to RV park and when we arrived, turned on Rear AC and it worked.

After first day at the park the AC stopped working again. So I called a local mobile RV mechanic to come take a look at it.

NOTE: We were in Destin Florida at Camping on the Gulf RV park. Called Lacey's RV Service. Travis Smith is the owner. (850-859-2262) I called Travis late in the day (4:00pm) and figured it would be the next day before he could get to us. However, he said no problem he could swing by but it would be late. What service!!

Travis went into the back bedroom, removed the AC cover and immediately said "I see the problem".
The problem was the thin foam sheets that are used to separate the air inlet and outlet were not sealed properly. Obviously over time they had started to come loose and there was actually a small hole in one of the sheets. The AC needs to have the air inlet and outlet sealed off from each other to prevent freeze ups. There are 2 covers on the AC, so he took the other AC cover off and used Foil Duct Tape to completely seal the foam sheets between the air inlet and outlet. Put it back together and the AC worked for the next 2 weeks while were are the beach.

So if you are in a hot environment and your AC is freezing up this is the first thing you might check. I have watched a number of YouTube videos where people use Rigid Foam Board Insulation and foil duct tape to better seal the air inlet and outlet on their AC units. This also assists with the unit running more efficiently.

Anyway, wanted to share this experience in case someone else runs into a similar problem.

Keith and Jana Escue
2018 Montana 381TH
2016 Ford F350 King Ranch
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Old 05-25-2023, 07:59 PM   #2
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Join Date: Aug 2007
Location: Omaha
Posts: 6,667
M.O.C. #7560
Good information Keith! A lot of the times the fan is set wrong and that is what is making the unit freeze up and either start blowing warm air or stop running totally until the ice melts off and it will run again.
Thanks for telling us about the inlet/outlet situation and I'm sure it will get be of info to anyone experiencing the same problems.
Rondo is offline   Reply With Quote

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