Just replaced A/C gasket. How much do I compress it with screws before stopping?

[scottandanna]

I am sure the A/C needs to be elevated off the roof a bit to prevent damaging the roof.

But what is the general consensus on when to stop tightening the four long mounting bolts?

[slowmachine]

In the Dometic installation manual, there is a torque specification for the bolts. It is in inch-pounds, and the number is small.


Mike
2000 HR Endeavor

[scottandanna]

I think I have that out in my trailer. Will see if I can find that figure.

Thanks!

[scottandanna]

I don't have any documentation showing torque values. Anyone have access to this?

Mines a coleman, not that I think that makes any difference.

Also, should I use locktite? I have read that these things get loose all the time. Or is that just the foam compressing with age?

[slowmachine]

The Dometic manuals that I have say 40-50 inch-pounds, enough to compress the gasket about 1/2". No thread locker.


Mike
2000 HR Endeavor

[Old-Biscuit]

The 4 hold down bolts should be tightened by finger in an 'X' pattern until 'snug'

The torque valve you is in INCH Pounds and is 40/INCH LBS

The new roof gasket is 1" thick and when properly torqued down it will be compressed by half ----A/C pan should be elevated above roof so that rain/water/evap drip pan run off can flow around/under A/C pan and not accumulate.

The hold down bolts should be dry...no lubricant--no locktite etc.

After installation of a new roof gasket you should check the 'tightness' of the 4 hold down bolts after couple trips (traveling will set gasket).

40 INCH LBS -----------OR just 'SNUG'

[slowmachine]

At least one Coleman manual shows a "gasket indicating tab" for measuring gasket compression.

Manuals here:
Document Library

[mel s]

Originally Posted by scottandanna

I am sure the A/C needs to be elevated off the roof a bit to prevent damaging the roof.

But what is the general consensus on when to stop tightening the four long mounting bolts?

scottandanna
You can find the torque specs for the hold down bolts of your particular make and model of A/C unit in the A/C owners manual for your A/C unit....(mine specifies 40-50 INCH/pounds).

(BTW I check mine every year or 2 with a Harbor Freight 1/4 drive inch/pound torque wrench and often find they need to be re-torqued).
1/4" Torque Wrench - 20-200 in. lbs.

Mel
'96 Safari, 147k miles, (mine since '01)

[scottandanna]

Thanks for all the info! Exactly what I needed!

[Old Scout]

Probably too late for this go around--but there are two kinds of gaskets on the market: 1--the cheap, white one that will crush almost immediately; and 2--the more expensive [about $20] gray one that is made from close cell foam--much better. For A/Cs with exterior drain cups--you can / should use two gaskets. Also, since many units are sort of cantilivered over the 14" opening, be sure to use the outboard foam blocks, which come with some gasket kits, on the perimeter of the unit to distribute weight.

[scottandanna]

Yes, too late, I ended up with a white one, and it felt WAY flimsier than the gray one I removed.

I actually never saw any of the gray ones while I was shopping for a new one. This will work for a few years, and I will search out a gray one next time.

My kit did come with those couple extra pieces to distribute the heavy rear weight.

[Ray,IN]

Originally Posted by slowmachine

In the Dometic installation manual, there is a torque specification for the bolts. It is in inch-pounds, and the number is small.


Mike
2000 HR Endeavor

40-50 in/lb for a Dometic Duo-therm.Page 13

[scottandanna]

Gasket indicating tabs....that would be the yellow tabs that were attached when I disassembled, then. I might still be able to find and re-use them.

Bought a 20-200 in/lb torque wrench. I had nothing that small in my toolbox. It will stay in the trailer's toolbox, and I will check it every year or so.

EDIT--found one, it is 5/8" thick, so I can at least stick a tape measure up there and measure the gap. I may look around and see if I can find all four and reuse them. Wish I had known what they were before I took it all apart.

[slowmachine]

Originally Posted by scottandanna

Gasket indicating tabs....that would be the yellow tabs that were attached when I disassembled, then. I might still be able to find and re-use them.

Bought a 20-200 in/lb torque wrench. I had nothing that small in my toolbox. It will stay in the trailer's toolbox, and I will check it every year or so.

EDIT--found one, it is 5/8" thick, so I can at least stick a tape measure up there and measure the gap. I may look around and see if I can find all four and reuse them. Wish I had known what they were before I took it all apart.

I like the idea of the tabs better than using tiny torque values. The tabs measure gasket compression, which is a more consistent method of creating uniform pressure around the perimeter of the seal. Torque values, especially small numbers on large-diameter bolts, can be skewed significantly by debris in the threads or damage to the threads themselves.