83 HR...A/C out with an axe?

[hpbcrillo]

Well, that's not how I would do it, but it looks like the PO did it. You will see some pics of some huge dents and gashes through the alum roof further down. I noticed a small drip coming from the front o/h ac unit (ac not running) and decided to see if the gasket might need tightened up. What I found was NOT GOOD. I plan to keep posting here for my renovation thread if that's ok. Let's start with some pics of our baby. 1983 HR Aluma Lite, 454 engine, 30' long, one owner (before us)

[hpbcrillo]

When I got the AC cover off, what an adventure! They used wood 2 x 4's to attach the cover to, since it was made for a different model of AC unit. Then in their attempt to stop the leak, they decided to silicone EVERYTHING they could see up there, including the 2x4 wood brackets. What a mess! It had held water in so long, the bottom of the AC unit was rusting. They must have spent a lot of money over the years on silicone sealant and caulk and repair tape. If you look at the last pic, you can see where they tried to seal everything from the inside with silicone. And see the alum vent that they crushed by overtightening the mounting bolts without aligning it with the bottom vent opening. Just proves that when you don't address the source of the problem, you just make things worse.

[hpbcrillo]

The inside was bad, but the outside was horrible! I'm sure you have run across worse, but without pulling the AC unit, you would never know what was under there that needs redoing. So I started peeling off the old silicone and caulking, and scraping. I couldn't find any remnant of the old gasket, just gobs and gobs of silicone, etc. Mounds and mounds of sealant, and it still leaked.

[hpbcrillo]

I continued to scrape and clean with Acetone (alum roof) and made some progress, slowly. Fortunately we don't have bad weather yet. The aluminum edge was crushed, torn, wrinkled, stretched and distorted, so I resorted to my bodywork tools to try to flatten it back out. (got a couple pics out of order, show the wood 2x4 with silicone sealing)

[hpbcrillo]

But now we are starting to make some headway. First is the large gash in the roof. they just pooled silicone in it, but I think that spot was leaking also. I plan to fill the void with bondo underneath, then flatten the aluminum skin, and cover with eternabond tape. You can then see how it was starting to clean up. The next step was to fabricate a stainless steel frame to allow the AC gasket to seal properly (the ss is nice and flat and thick). I will end up sealing the ss to the alum roof with Eternabond sealing tape also. But to make the ss frame, I had to dig out my trusty plasma cutter, which did a great job!

[hpbcrillo]

I had a ss prep table with 14 gauge ss to use to make the ss frame. I then ground down the edges smooth. After locating it on the roof and marking the border, I began putting down 2 layers of eternabond doublesided sealing tape, to allow the flat ss frame to seal to the irregular edge of the mangled aluminum roof material. Then I applied the ss frame to the eternabond...and it is stuck! As I mentioned earlier, there will be a 6" wide layer of white eternabond tape sealing the top of the ss frame to the top of the aluminum roof. (I have a bit more cleaning and removing of sealant first).

[hpbcrillo]

And here is where I left off. I attached the new AC sealing gasket to the ss frame, since that is a great, flat, clean and solid surface for the gasket to adhere to. I know that the standard approach is to attach the gasket to the AC unit, but I have a couple reasons for doing it this way. 1) there were a couple small pieces of the old gasket remaining on the aluminum roof...below gobs of silicone...and that old gasket was the hardest thing to remove from the aluminum. It really stuck great. And since any water that tries to infiltrate the rv will be at the bottom edge of the gasket, it made sense to seal that edge of the gasket to the ss frame.2) If you remember how rusty the AC unit is, I probably would not get good adhesion to it. I do plan to sand and treat the rust, and apply several coats of paint to weatherproof it before setting it on the gasket. My next step is to remove the mangled air vent and straighten it out before reapplying.
Thanks for looking, and please give me any advice, as this is our first rv. I have already learned so much from this forum, and saved hundreds of dollars and hours of frustration by learning from all of you. Thank you! TO BE CONTINUED......

[dmurdock]

Looks like you're on the right track! Not sure what your plans are but I'd go hog wild with self-leveling sealant between the stainless and the roof (may want to wire wheel the stainless to rough up the surface). I'd also wire wheel the rust on the a/c then paint it with that rust activator goop (that stuff that turns rust purple). If you can use some scrap steel to fab some mounts for the cover that would be best as that wood was probably interfering with airflow to a degree and is a moisture magnet (especially untreated on the outside like that).

[hpbcrillo]

Originally Posted by dmurdock

Looks like you're on the right track! Not sure what your plans are but I'd go hog wild with self-leveling sealant between the stainless and the roof (may want to wire wheel the stainless to rough up the surface). I'd also wire wheel the rust on the a/c then paint it with that rust activator goop (that stuff that turns rust purple). If you can use some scrap steel to fab some mounts for the cover that would be best as that wood was probably interfering with airflow to a degree and is a moisture magnet (especially untreated on the outside like that).

Thank you so much! I actually thought about using a wire wheel (carefully) last night, and I think it will help. I also have the eternabond cleaner and primer that I plan to use before applying the tape.
Your suggestion of how to treat the rust on the AC unit is great. That is how I will attack it.
And for your suggestion to get rid of the wood, I think I will have to do that. I hadn't thought about the airflow or moisture retention. I can fabricate some metal brackets to attach it to the AC unit.
Again, thank you for those great ideas....that's why I love this forum. The help and sharing is awesome. Have a great day!

[dmurdock]

Or a wire brush if it's really thin metal..basically get the rust down to where the rust is well adhered to the surface and not loose or flaky.

This is the type of stuff I'm talking about:

http://www.amazon.com/VHT-SP229-Rust.../dp/B002NUABUO

http://www.amazon.com/dp/B001000VS0?psc=1

You want something that actually chemically bonds with the rust not something that just "sticks" to rust.

Good Luck!

[Geocritter]

Wow, I enjoyed your photos, very enlightening! You're doing a great job correcting Goober's handy work! It's also somewhat of a comfort to me to know that the original owner of your RV was apparently even dumber than the guy who originally owned my RV.


Steve

[stumpnc]

After you get the old A/C unit base cleaned,apply a coat of Ospho to neutralize the rust.
Ospho

[hpbcrillo]

Originally Posted by stumpnc

After you get the old A/C unit base cleaned,apply a coat of Ospho to neutralize the rust.
Ospho

Yep, that is what I'm gonna use. great stuff! Thanks!

[spritz]

Great write up and great pictures,
Thanks,
Tim