Rooftop A/C drips when running

[BobBeery]

After 4 months owning an 87 Dolphin I finally needed to use the air. Until now I had only run it for a minute to feel the first cool air when I bought this rig. The wonderful cold air came blowing in but a couple minutes later water started dripping from the rear louver. I got a big drop every couple of seconds. (Note I have had hard rain both parked and when driving with no leaks.) I turned the unit off and pulled the plastic bottom off, which had water in it. I found the path the water took came from between two metal pieces, the lower piece running fore-and-aft and appearing to be part of a clamp frame to pull the unit down against the roof. The air duct for the cold air was dry on the inside and had only a trace of moisture beads on the outside. I have no ladder and was not able to get on the roof for a look. I had the owners manual and installation directions but found nothing about this situation. This is a Coleman unit, I cannot tell you more now because I loaned the Toy to my brother. Is there supposed to be a drain for condensate which dumps onto the roof? Could it be plugged, perhaps by the gasket or some over-enthusiastic caulking? Where would such a drain be located? Or could a catch-tray which feeds such a drain be missing? Where would I look? The local RV repair shop is competent but at $65 an hour.

Edited July 24, 2010 by BobBeery

[Maineah]

I would pull the cover off the top of the A/C and check to make sure nothing is plugged. It really is a simple task to remove the entire unit and the gasket set is only about $15. The gasket shrinks over time and the A/C unit will settle down on the roof. There are two bolts under the inside cover and a wiring box just remove the two bolts disconnect the wiring and the unit will lift off.

[BobBeery]

I finally got on the roof and removed the shroud for a look. There is silicone caulk all the way around the metal base, so condensate is trapped between the correct a/c gasket and the silicone on the perimeter. I intend to take up the unit, remove all silicone, and replace the gasket. I think I understand getting the unit off and on from other posts, but want to be sure I get the gasket install correct. So question: does anything go between the roof and the gasket? Does anything go between the gasket and the a/c unit? My roof is painted aluminum with slight flat corrugation (87 Dolphin). A cross section looks like this _______________-------_________________-------. The raised section is about a sixteenth of an inch higher than the unraised section. There is nothing under the raised part to keep it raised; it is easily pushed down except at the bends. Any advice??

[Maineah]

The caulk should not be there some one did the same thing to mine and it was a pain to get off! The gasket has a sticky side that goes down there is also a piece that fits under the back of the unit to keep every thing on an even plane. The gasket is quite thick and will conform to the surface.

[BobBeery]

Today I replaced the gasket. Thanks Maineh for telling me what the extra piece of gasket was for. I got all the silicone up that encircled the base, that was a chore. It was really stuck to the roof. Found lots of rust on the underside of the roof unit because the silicone wouldn't let water out. The old gasket must have been only a quarter of an inch thick, and had been stuck to the underside of the a/c. When I peeled the old gasket off the sticky clear tape stayed on the underside. I couldn't get it to peel. Then I had to decide if I should stick the new gasket sticky side to the roof as Maineh suggested, or to the a/c as the old gasket was. I ended up sticking it on the roof. There was a problem setting the a/c back in place. I put it down about 3/8 of an inch to the right, then had trouble moving it over because it stuck to the new gasket. But I did manage to get it set right. tighten the inside mount, and try it out. I have cold. Have to wait for rain to see if I'm watertight. I'll have to remember next summer on a hot day to re-snug the bolts. It was only in the low 60's so the gasket was stiff and didn't compress as much as it will when it's 90.

[Maineah]

I think you'll find it's also quieter. Don't crank it down too tight maybe let it settle over the winter and snug it up next spring, the gasket does not need to be compressed too much or you maybe back where you started.

[p10leadman]

after an absence for over a year I'm back on this forum- the ac unit on the Odyssey motorhome seems to be a weak point. Mine is doing the exact same thing, and it too is sealed down all around with silicone, but worse yet, the rain comes thru the side grill and eventually goes between the ceiling and roof-oh whatta mess. the other ssue is the cab battery keeps going dead- we've replaced the alternator, the power charger / inverter, finall y gave in and installed a float charger 24x7...

[Derek up North]

I know it's 'the basics', but have you thought that perhaps the cab battery is bad and won't hold a charge?

[Gulfstream Greg]

Today I replaced the gasket. Thanks Maineh for telling me what the extra piece of gasket was for. I got all the silicone up that encircled the base, that was a chore. It was really stuck to the roof. Found lots of rust on the underside of the roof unit because the silicone wouldn't let water out. The old gasket must have been only a quarter of an inch thick, and had been stuck to the underside of the a/c. When I peeled the old gasket off the sticky clear tape stayed on the underside. I couldn't get it to peel. Then I had to decide if I should stick the new gasket sticky side to the roof as Maineh suggested, or to the a/c as the old gasket was. I ended up sticking it on the roof. There was a problem setting the a/c back in place. I put it down about 3/8 of an inch to the right, then had trouble moving it over because it stuck to the new gasket. But I did manage to get it set right. tighten the inside mount, and try it out. I have cold. Have to wait for rain to see if I'm watertight. I'll have to remember next summer on a hot day to re-snug the bolts. It was only in the low 60's so the gasket was stiff and didn't compress as much as it will when it's 90.

I may have been told wrong on how to install the gasket that I bought from a local RV repair facility. I was told that the sticky side sticks to the AC unit and I was given a special glue caulk for the roof side. The gasket kit also had two other straight pieces that went out on the ends to help stabilize it sitting on the roof. Wait for rain? How about a hose?