Skip to main content ↑ ↓
Topic: AC gasket-something to think about (Read 386 times) previous topic - next topic

AC gasket-something to think about

The gasket under our roof AC units come with instructions to place them on the bottom of the AC with the adhesive UP.
Yet, due to time(?) and shrinkage and the AC settling we are told to tighten the four bolts holding the AC on the roof. This usually after we experience a leak.
So why not put the gasket in place adhesive down and then caulk around the gasket where it meets the roof material?
Think about it. Water does not ever puddle deeper than the foam gasket on the flat roof of a motorhome, and as the AC settles due to time and shrinkage there is still a good seal between the AC and the gasket.
So? What do you think? Was this original design a mistake or just an easier way to get the gasket/hole/AC aligned?
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: AC gasket-something to think about

Reply #1 –
When we had NMS replace our original factory installed roof airs they found the gaskets were installed adhesive side down.  It took them a good bit of time on each one getting all the old gasket and glue scraped off the roof before they could install the new units.  So I would say one good reason to stick them to the A/C unit is simply to make future removal/replacement easier.

Other than that, can't see that it would make that much difference one way or the other.

I don't think caulking around the gasket should be necessary as long as it is installed following manufacturer instructions.  Tighten the bolts until the gasket is compressed to 1/2 it's original height, and you won't have any leaks.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: AC gasket-something to think about

Reply #2 –
Scraping off the AC or the roof is going to be required either way. Flipping the AC over to scrape it while up on the roof might not be very easy.
Just wondering.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: AC gasket-something to think about

Reply #3 –
My gaskets were already attached to the Atwood AC units that I installed last year.Although if they weren't I probably would have done what you said. I thought the holes in the roof were slightly larger than my gaskets no matter what I did I couldn't get them to line up exactly but we're only talking millimeters.
'99 U320 40 WTFE
Build #5462,
1500 Watts Solar 600 amp Victron lithium
2012 Jeep Grand Cherokee Overland Hemi
Instagram bobfnbw
Retired
 

Re: AC gasket-something to think about

Reply #4 –
Quote from: nitehawk –
Scraping off the AC or the roof is going to be required either way. Flipping the AC over to scrape it while up on the roof might not be very easy.
I was thinking more of when you need to replace the whole A/C unit with a new one.  In that case, gasket stuck to old A/C unit makes less work.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"