Dash AC Condensation Leak - Carpet Soaked!

[Fireman_898]

Ok guys I'm hoping y'all can help, I've done some research on here and other various forums and I've found very limited information specific to my problem. The issue: my 03' Diplomat is leaking dash AC condensation onto the passenger's side footwell soaking the carpet!

I’ve done the obvious: Detached the drain line from the bottom of the condenser unit and cleared it out, I’ve blown out the 90 degree elbow where the drain line attaches to the condenser, and I’ve even removed the condenser unit completely to check for additional blockages - to no avail.

Now this weekend while I had things apart I went ahead and removed the condenser and heater core unit from the nose of the coach. Things looked good for the most part, but there was some rust and debris in the bottom of the housing that could have been partially blocking the condensation from draining. I cleaned everything up and reinstalled the unit - the problem persists… I did make one important discovery though upon my reexamination, the carpet was not wet around the return intake grill on the passenger’s floor board, but rather it was wet right at the seam where the firewall meets the floor (could this be a clue?).

Now I have found a post or two about insulating the firewall, but I’m hoping that someone that has done this can shed a bit more light on the topic. My firewall is covered in a 1/4 to 1/2” soft cell foam which I would think would be enough insulation to keep it from condensing humidity. There is also a 3/8” piece of plywood on the inside of the firewall to which the carpet is attached. Surely between the foam and the wood, the metal firewall isn’t getting cold enough to condense that much moisture, right???

So when y’all said you insulated the firewall, did you actually add insulation to the firewall, or did you add it to the inner plate that secures the condenser and heater core to the housing? Did you insulate the exterior of the plastic housing too?

Looking at the firewall from the nose of the coach it does look like there is a seam where the firewall meets the floor. Do you think this is where my water leak is? If so should I just caulk or spray some “flex seal” over the seam with the condenser unit removed? If the recommendation is still to add insulation, where exactly should I start adding and what have y’all found that works best? Also, does anybody know what the asphalt like substance (black goo that is sticky as all get out) is called that is used to seal the condenser housing where the lines for both the condenser and heater core penetrate the housing?

Any suggestions will be greatly appreciated. I’ll be heading back out this weekend to do some more work on the coach and to hopefully fix this issue once and for all. I will also try to document the repairs this weekend to put a “how to” together for those of y’all that may someday need to replace either your heater core or condenser (it is always a good thing when others can benefit from my blood, sweat, choice words, and tears…)

As always this forum is the best and I look forward to the suggestions rolling in.

Thanks in advance!

[Skip426]

Pictures we love pictures, for your tutorial. Sorry can't help just had to throw that in. Good luck finding your problem.

[stink]

Might suggest extending the condensate drain line outside. The condensate may be getting blown back and leaking back in at the lower seam. Just a thaught?

[falconman]

You did pressure check the heater core?

[Gorlininc]

My leak was the drain on the AC unit. It's really the only water around that area. The heater core is also in that area. Is try bypassing the heater core. Then the only thing left us the AC

[jonohio]

pictures? I may have a similar issue but not sure what's what under there.

[Fireman_898]

Thanks everyone keep the suggestions coming...

I have checked and the heater core is in excellent shape - no leaks. The moisture is definitely condensation as it doesn't appear unless I'm running the AC - no moisture while running the heater.

I can see condensation draining from the drain line, but I also see moisture right underneath the condenser housing, like not all of the condensation is going out the drain. I'm not sure what I can do to keep that from happening (i.e. insulation, sealant, etc.).

I'll swing by the rig tomorrow and take a few pictures so y'all can see what I'm seeing.

Thanks again to all who have replied, I'll report back tomorrow.

[walt2137]

Colin i had that same problem with a 99 Dip, what happened is Monaco failed to insulate the metal firewall and the cold air in the AC box blowing on the metal firewall makes water and the only solution that i could find is pull the plastic box off and insulate the fire wall, you will find that the two screws next to the front cap passenger side will be tough to get to and remove but it is doable. I had a write up on the procedure but cant find it.

[Fireman_898]

So here are a few pics of the problem area. At the bottom of the condenser housing you can see a line of rust. This is where the water seems to be pooling, but I'm not sure if this is where it is entering the coach. What do y'all think? I picked up some insulation this evening. I think I'll go ahead and add some extra insulation between the condenser unit and the firewall as suggested and try to seal the seam where the fine line of rust is. Any other things I should try while I've got it back apart this weekend?

Thanks again to all that have replied. I will take pictures and post my findings post-repair.




Colin & Abbie

2003 Monaco Diplomat PST
2007 GMC Sierra Classic 2500HD Toad

[avfordguy]

I have a 04 dip PST and I will post some pics tomorrow of the area of carpet that gets wet, now mind you I never had the issue in CA just when I moved to TX did it show up ( in high humidity places). mine does not seem as rusted as yours ( 50K miles ) so something is going on. Also I might add that I never had the issue until I evac'ed and recharged the dash a/c with the correct amount of R134, before I had discharge temps in the mid 50's now I have discharge temps in the mid 40's. A lot depends on the "dewpoint" temp inside the coach.

[walt2137]

Its a good possibility that the carpet was geting wet under the center drawer and you could not tell.

[Stan&Jacquie]

Colin, I had a similar problem with my 2007 Knight. I discovered that whenever I found the carpet under the dash on the passenger side getting wet, I could reach up under the dash and run my hand along the round duct to find water dripping off of it. I wrapped the entire duct tube with foil backed thermal wrap (Home Depot, wrap for sweating pipes) and the problem stopped. I can only deduce that the uninsulated ac duct (plastic hose) would sweat when cold and drip onto the floor.

[avfordguy]

I had the problem of sweating a/c coponents making the carpet wet,now mind you i have moved from the desert of CA to south texas (corpus christi area), so i am fully aware of high humidity. I will post some pics tomorrow on how i reduced ( not eliminate) the problem.

[Stan&Jacquie]

Originally Posted by avfordguy

I had the problem of sweating a/c coponents making the carpet wet,now mind you i have moved from the desert of CA to south texas (corpus christi area), so i am fully aware of high humidity. I will post some pics tomorrow on how i reduced ( not eliminate) the problem.

That will be most helpful. Many thanks!


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