A/C Leak, Not From Foam Seal

[Gary Cunningham]

Dometic Duo-Therm A/C often soaks the bed during a move. Even in the worst rain storms with wind blowing hard, no leaks. Only after we move the coach do we sometimes find the bedding soaked under the lower unit. Unit was replaced 2 years ago, twice tightened the unit (gently) as was recommended by the installer. I'm unable to remember if it is only after the unit has been run, or only after a rain that this occurs. Ample condensate runs off the roof. (Sadly, the installer didn't replace the drain 'cups' and allow for the condensate to flow thru the lines as designed by the factory. He told us they only clog up and cause problems. Smarter now, but too late to the dance.)

 

Since there doesn't seem to be any way for external water to get into the cutout, I believe it must accumulate somewhere, and then spill out when we move the rig. However, it has never accumulated to the point of getting wet while we are stationary for months at a time.

 

Puzzling to me, maybe you have a good idea?

[justRich]

We had an Arctic Fox truck camper that while on the humid Mexican west coast would drip water.

That AC unit depended on evaporation for condensate to go away. But in high humidity, the moisture would condensate enough to fill the AC drip pan. I could rock the camper enough to make it spill into the camper.

Back in the states, I removed the AC shroud and could find no drain or weep holes. That observation meant that condensate would not evaporate fast enough and would drip into the AC bottom pan - eventually filling the pan and dripping into the camper.

I drilled holes into the bottom of the drip pan to cure the problem.

Unfortunately, I traded the camper before I ever had a chance to get into high humidity, high temperatures again.

The drip holes were never tested.

[Ray,IN]

It's possible to have an air leak between chilled air output plenum and warm air intake plenum. This results in, #1- reduced cooling from unit, #2- condensation on/near the divider between the plenums.

[Kirk W]

I suspect that the problem is condensate that isn't draining completely from the unit and then empties on your bed when you travel. Start by making sure that the drains are clear so that the condensate can all drain out as it may be that it has to fill partially before it runs out, or that not all of it runs out.

 

I am also wondering if the entire bed is wet, or is it just a spot on the bed?

[Gary Cunningham]

I am also wondering if the entire bed is wet, or is it just a spot on the bed?

Just the area under the lower unit becomes saturated.

 

For Ray: What would be the correction for your theory?

Thanx,

[Kirk W]

What would be the correction for your theory?

I suspect that removing the shroud and accessing the drains would be the best place to start. If it is holding some water in the condensation catch tray, as it seems, then you need to figure out why that is happening and correct it. If the tech left part of the drains out, that is very likely related to your problem.

[oldjohnt]

Id crawl up on the roof armed with my air pressure blow gun, remove the cover and look for any (if so equipped) clogged up condensation drain holes and open them. While up there clean things up and oil the fan if so equipped. Make sure some "dude" didn't get caulk crazy and seal over where things shouldn't be. Off topic but I owned so many flat roofed Class C's over the years where the AC settled down into a slump that I braced and rigged up the roof and lifted its center maybe 1/2 inch and they never leaked around the AC thereafter, but looks like yours may be failure of condensation draining.

 

John T

[Gary Cunningham]

Okay, good points. I'll get up there tomorrow and see what can be seen. I'm curious, if it is condensation not draining from where it accumulates, why it wouldn't overflow to inside during conditioning, only when jostled?

[Kirk W]

Since we are not there but only guessing, my best guess is that it partially drains, leaving some water to evaporate or to be spilled on your bed when you travel.

[Ray,IN]

Just the area under the lower unit becomes saturated.

 

For Ray: What would be the correction for your theory?

Thanx,

 

Remove inner/lower unit for complete access to the under-side of the A/C unit. You will see a sheet metal divider between warm air intake and chilled air outflow. Any/All gaps must be sealed with metal duct-tape so any cross-flow of air is eliminated. The lower unit completes this seal when re-installed.

I experienced that with our 2005 5th wheel roof units. I sealed that sheet metal divider to eliminate any cross-flow, A/C /heat pump performance was greatly improved.

 

Do remove the outer unit shroud and inspect the drip pan under the condensing coil. It is constructed to retain some water. This water improves operation of the condensing coil; BUT if the drain hole becomes it overflows that pan, and if the holes in the large bottom pan of the unit become clogged also, all condensate is forced to go elsewhere. If that is happening you should have much more than a wet spot on the bed.

This is also a great time to disconnect the A/C unit from power, clean out both pans and insure all drain holes are open. I have discovered leaves, wasp nests, mud-dabber nests on fan blades, etc. Clean and straighten fins on both evaporator and condenser coils.

[Gary Cunningham]

Just came down from checking the unit. The plastic condenser-surround is clean, and the holes at each end are clear. I didn't see where to oil the fan motor, but for now everything turns freely. All the large pan drains are completely clear and everything was clean. The only thing I saw that was amiss was the top plastic shroud (under the Styrofoam) which is clipped and screwed on . It was cocked up in one corner about 3/8", and that clip wasn't snapped. It took a couple self-tap screws to get that corner to stay back down. Cannot see that having any contribution to the bed wetting problem I've described though.

 

Still a puzzlement!

[Kirk W]

That would seem to eliminate the drains, but the symptom still sounds like a problem of some "saved" condensation. If there has been no rain but it still wets your bed, I don't see what else it could be..... Have you been able to pin down just where the water leaves the a/c unit? Perhaps have someone lay on the bed when you start to travel and watch for it to drip out so that you can know for sure what the entry point is.

[Gary Cunningham]

It's been a while I know, but here is the final answer as of earlier this week.  Our Tiffin was made with an A/C drain line built into the roof, which channels the condensate back and down past the engine.  Both A/Cs share the same line.  When my rear A/C was replaced, the installer didn't use the old collection pans or connect the A/C to drain into the built in drain line.  I discovered that line was partially clogged at the bottom of the pipe, allowing just enough through from the front A/C to not spill out of the line over the bed UNTIL the rig was moved.  Must have been a half gallon of water come out of the line once unplugged.  Now water does not build up in the line by the rear A/C and does not wet the bed.  Thought somebody might be curious about the final answer.  My thanks to those who tried to help!

[Kirk W]

21 hours ago, Gary Cunningham said:

Thought somebody might be curious about the final answer.

Thanks for coming back to let us all know! And you thought that you were finished with bed wetting when your kids left home!