Coleman AC Leaks in Heavy Rain

**Dave Jenkins** · 06-04-2021, 09:04 AM

If the Coleman AC in the bedroom of our GD 320MKS is set on fan or AC it leaks water onto our bed in very heavy rain. Is this a known problem with these units? Any thoughts or experiences to share?

**FT4NOW** · 06-04-2021, 09:09 AM

If you remove the interior shroud of the AC there should be 4 nuts that provide the clamping force to hold the AC to the roof. They probably need to be tightened. Look up your particular model number to get the torque value. It is typically in in-lbs for those nuts, so you'll need a smaller range torque wrench.

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**Big Blue** · 06-04-2021, 01:36 PM

Just installed a Coleman Mach 3 in the bedroom of my 230RL There are tabs on the crush seal.... tighten 4 bolts until tabs touch the roof.... Also while waiting for help to put the new unit on the roof, I did a though inspection, and noticed a seam in the pan the compressor sits on.... I applied sealant to the seam as a precaution...

**DECelt** · 06-05-2021, 06:24 AM

I've not had any issues with my Coleman, but from my experiences with Dometic (the 2016 air conditioner from hell) checking the gasket torque would be the first thing that I would think of to do. While doing that, ensure that the temperature probe is properly inserted in the fins. This serves to prevent extreme icing. Icing can also cause those interior leaks, particularly in humid conditions. If neither of those areas are problematic then closely check the plenum area to ensure proper sealing and separation of intake and exhaust air. If that is fine, then check for leaks from the exterior of the ac unit frame into the plenum using a light source.

Troubleshooting these can be difficult as you can have two leak sources and assume that they are the same leak.

**geotex1** · 06-05-2021, 06:56 AM

Worst case, get a fresh gasket. It is a pain to disconnect the wiring and pull the foil tape, but a new gasket, A/C centered in opening, torqued properly, and the re-taped should cure it. The important thing is to fix it fast because it is leaking with any rain, and the water you are not seeing till it's heavy is the water to worry about.

**RML850** · 09-09-2021, 09:02 AM

Same issue with 2021 29RS rear mounted Coleman A/C unit. Tightening mount bolts did not help. Solution was to turn unit off during heavy rain. If the tray that catches condensation gets plugged with debris the same thing happens, but my tray was clean. I believe the A/C fan, when running, pulls in enough extra water during heavy rain to overflow the tray. I’ve been through many heavy rains since with no more leaks.

**Redapple63** · 09-09-2021, 08:54 PM

Originally Posted by geotex1

Worst case, get a fresh gasket. It is a pain to disconnect the wiring and pull the foil tape, but a new gasket, A/C centered in opening, torqued properly, and the re-taped should cure it. The important thing is to fix it fast because it is leaking with any rain, and the water you are not seeing till it's heavy is the water to worry about.

This is the best permanent solution.

**DECelt** · 09-10-2021, 06:49 AM

Originally Posted by RML850

Same issue with 2021 29RS rear mounted Coleman A/C unit. Tightening mount bolts did not help. Solution was to turn unit off during heavy rain. If the tray that catches condensation gets plugged with debris the same thing happens, but my tray was clean. I believe the A/C fan, when running, pulls in enough extra water during heavy rain to overflow the tray. I’ve been through many heavy rains since with no more leaks.

You're dead on!

We had a similar issue with our 2016 dometic AC's on our old rig. The culprit was the seam where the top cover set onto the bottom cover...allowing lots of water in. I taped those seams and never had another issue. These acs had been reinstalled at the factory....so gaskets etc were not the issue.

You would think they would design a rooftop ac to not be do vulnerable to rain!

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