5th wheel AC leak

[RobertN]

I keep getting a leak at the AC unit on my 5th wheel.

We got it used three years ago. Unfortunately, near the end of our 4500 mile round trip to Texas right after we got it, the rubber roof liner went on us(peeled back 10' while we were on I-5). So, I learned how to replace a rubber roof with help from a couple friends that had worked in RV repair. Everything about the roof replacement has worked great, except the AC unit.

The first year after the roof replacement, I got a leak. Tightened it down, and that helped for a while. Wound up having to replace the foam seal. That worked thru last year. Now, I have a leak again. Nothing changed on the AC unit. When I replaced the seal last year, the roof looked and felt nice and flat where the AC mounts.

The seal is compressed about 1/2 way, like the directions say(I have all the original paperwork for the AC, including installation). If I tighten it more, it will tighten the AC weep holes will be against the rubber roof.

My wife thinks we should just caulk around the seal.. The directions don't say to do that, and neither did my RV repair buddies(have lost contact with them; they both moved).

I'm not sure what to do...

Anyone had a solution to a problem like this? I'll try to get some pictures in the AM.

 

[Stihlrunner]

Are you sure that it is coming in around the seal? Most modern RV roof frames are many sections of box tubing welded together, it's easy for a leak to travel inside a tubing and come out somewhere else.

With almost 20 years RV repair experience, I can say that on older RV's with uneven roof surfaces or sagging braces around the AC it can be necessary to apply silicone around the gasket before lowering onto the roof. However, this is not necessary on a roof in good shape.

Could it possibly be condensation?

If you have a decent RV repair facility near you, inquire if they have a SealTech machine. This is a machine that attaches to a roof opening and creates a positive pressure in the RV, forcing air out potential leak points. The tech goes over the RV with a soapy water solution and bubbles show at trouble spots.

Can you give more information as to the conditions when the leak occurs?

 

[RobertN]

It did not leak for a while after I snugged the AC down tighter. I was wrong above; I followed the directions both times reinstalling the AC with new gasket; the book says it should compress the gasket 1/4".

That 1/4" just did not seem to be enough. After a year with a few trips to the coast, it settled, both times it would seem.

The 5th wheel is a '98. The roof is good; the wood etc is solid.

It leaks when it rains. We only used it really on our first trip, before the rubber roof peeled back on the highway. Most of our trips are to the N. Calif coast, where dont need AC...

 

[Diamondpilot]

I would remove and install again with a new gasket or better yet two. We use the same units on house boats and always apply a big bead of silicon, I am talking 5/8" or so, before setting it in place.

Chris

 

[RobertN]

This is one of the only pictures I have... From when we first got it. I'll try to get more today of the AC unit, but it is raining...

 

[kenmac]

if you have a rubber roof. Don't use silicone. I use eternabond products and have had great results

 

[RobertN]

I was wondering about that. I still have a tube of the caulking used around vents and screws(the kind that "flows"). I don't think that stuff would work.

There are a couple RV places local; they must have "caulk" like that. Rubber roofs are on everything... I want to start with new seals anyway.

if you have a rubber roof. Don't use silicone. I use eternabond products and have had great results

 

[kenmac]

I order mine on line. Just ordered 4 more tubes to have around ( $33.00 with shipping). They (eternabond) also has a tape that I have used to seal around the front & rear cap & vents. I believe I used the tape around my A/C unit as well

 

[Stihlrunner]

There is nothing inherently wrong using silicone under the AC gasket. Silicone is not the correct sealant for the roof seams or attachments, for that you need a self-levelling elastomaric sealant that is compatible with your rubber roof. I don't use self-levelling sealant under attachments because it never really dries.

Most RV's use Alpha sealants on rubber roof material, sometimes Schnee-Morehead.

 

[kenmac]

I have used self leveling .I didn't like it. I like the eternabond brand caulk. I must have missunderstood. I thought silicone was going to be used on the outside area around the the A/C flange ??? where it meets the rubber roof.