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Old 07-17-2013, 10:01 AM   #1
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1997 25' Excella
Waterville , Minnesota
Join Date: May 2013
Posts: 44
Did I make a Boo Boo?????

I was reading threads about air conditioning problems on this site, only trying to find out where my drain tube (outside) would be on my 25' excella, and saw several people chiming in on "dont use caulking on your ac", well, I may have done it this time, a month or so ago I removed/redid caulking on top and sides of mine. Around the ac unit the PO had "used up" the last of a tube of caulking around where the unit meets the roof, so peeled off the old and replaced it, well, I hope I didnt mess the drain system up any since I saw some drained to the top of the roof instead of a tube. Whats the concensus on this one???

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Old 07-17-2013, 10:06 AM   #2
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2012 30' International
Walkerton , Virginia
Join Date: Dec 2003
Posts: 2,370
The advice is not "don't use caulking", but "don't use silicone caulking on aluminum".

Search sikaflex or vulkem on this forum and you'll find much discussion. The issue with silicone is that it etches aluminum, so prevents a good seal - and is devilishly hard to remove.


Somebody, please, point me to the road.

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Old 07-17-2013, 10:20 AM   #3
2 Rivet Member
1997 25' Excella
Waterville , Minnesota
Join Date: May 2013
Posts: 44
thanks for the quick reply, I did use the "good stuff" but was wondering if I should take it off??
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Old 07-17-2013, 10:22 AM   #4
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If you have a Dometic with the curved drain pan you need to be careful not to get caulk in the drainage channels. I cut away a small section of the roof gasket on mine so that it didn't block flow of the condensate to the center drain location.
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Old 07-17-2013, 10:40 AM   #5
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Naples, FL , Hood River, OR
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The only 'caulking' that was used by Airstream on roof A/C units was to seal their proprietary drain pan to the roof. No other sealants were used in the mounting process.

No other RV manufacturer: (1) uses a plastic drain pan and (2) does not use ANY sealant to secure a roof A/C unit to the roof.

Newer model Airstreams have in fact done away with this problem prone drain pan and have started using Dometic's Auxiliary Drain Kit #3107688.016. The roof unit is clamped to the roof using a pair of stacked 1" thick rubberized foam sealing gaskets that are then compressed to 50% of their original thickness when the mounting bolts from the bottom flange are properly tightened.

The only 'sealant' used in this application is to close the channels cut into the upper gasket to allow the drain hose to pass thru.
Lew Farber...RVIA Certified Master Tech...ABYC Certified Master Marine Electrician
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