Community Forums

BobJones · 11-17-2020, 05:07 PM

Hi guys!

I think I need new AC unit gaskets on my 2000 Diplomat. They are Duotherm (?) units.

Do I need the serial numbers off the units to get the right ones and what company made them?

Any other info on how hard it is to do etc would be appreciated.

JerryLook · 11-17-2020, 05:20 PM

My units are Dometic DuoTherm 600315.321. My gaskets aren’t leaking but I can see they are really compressed when looking at them from the side.

I recently contacted Dometic about seeing if I can add heat strips. They said no. While I was in email contact I asked them what is the gasket number for my units. They said it’s P/N 3313107.021. When I looked that up it looks like just a 16” strip, so I’m not sure that’s correct.

Most other kits I see show a 14” square gasket for around 34$. But I need to verify with Dometic that the number they sent me is correct.

Here’s a link to the other one. I’m not sure it will fit but it looks like the correct gasket. I just emailed them back today and will see what they say.

My AC part number was above where the filter mounts, and it was partially covered by a gasket.

https://www.amazon.com/Dometic-33107.../dp/B005BOQSEW

BobJones · 11-17-2020, 05:21 PM

OK, So I'm guessing the gaskets come from Dometic and to get the right ones I have to go on the roof and remove the cover to get the numbers off the units?

At that point I can find the right ones?

JerryLook · 11-17-2020, 05:24 PM

I’ve also read that you should use spacers when replacing the gasket so it doesn’t get compressed too much. I’m not sure if these spacers come with the gasket or not.

The P/N on mine were visible from inside the RV. Take the filter cover off and look directly up. It has a data plate looking sticker.

vito.a · 11-17-2020, 05:26 PM

RV A/C units use a standard 14" x 14"opening. This is the same size as RV roof vents.
The exceptions are Newmar coaches use a different return system (same gasket) and motor homes with drains under the A/C will require a double set of gaskets.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

To change the gaskets you will access four long bolts (7/16" hex head) from inside the motorhome. Remove the four bolts and the A/C unit will lift up. I recommend cleaning the old gasket thoroughly before sticking on the new one. Be careful tightening the four bolts. The spec is in inch pounds.

BobJones · 11-17-2020, 06:09 PM

Thanks guys!

Vito, my AC units are, as far as I know, standard. The drains are above the seal. They drain into a drip pan that has a plastic elbow on the side and then it flows onto the roof. This happens from above the gasket.

Given that information do you think it's safe to just buy two of the gaskets you linked to?

Lastly, I'm guessing you unplug the electrical connectors going to the A/C unit, pick it up, put it off to the side, clean up the hole, place the seal, and then gently put the AC unit back on top, plug it back in, torque to spec - and then Bob's your uncle?

(it's raining quite a bit up here so I need to do it smartly)

jacwjames · 11-17-2020, 06:23 PM

I'm going through the same thing, my front AC leaked ~ a month ago, I tightened the 4 bolts but plan on changing the gaskets.

I ordered a set of gaskets for both my AC units. My drip pans attach to tubes and drain through the coach so I had to get a set of the gaskets for the drip pans. I went ahead and bought the kit with the drip pans and will change if they don't look good, I know is cracked on the side.

From my understanding I believe you have to disconnect the AC unit and lift if off to change the gasket.

Not sure when I'll try and tackle this, I'll be watching this thread as you post.

Good Luck

vito.a · 11-17-2020, 06:42 PM

First trip the A/C breaker. There is a 120v wiring junction box accessed from underneath. Open the cover on it and disconnect the wire nuts. Then unplug the RJ11 telephone cord.
If you do not have drains then you should be able to lift the unit up after removing the four bolts. If you have drains they will T together underneath also. Disconnect the main drain line.
Sometimes these units have been glued down with silicone and you will have to break it loose.
After you place the unit back down on the new gasket you may want to tape up the junction from the ducts to the AC outlet with silver A/C tape.

The first one will take an hour and the second one about 20 min.

Step by step on replacing the unit. Just changing the gasket will be much simpler.
https://www.irv2.com/forums/f115/rep...ch-405503.html

BobJones · 11-17-2020, 06:56 PM

Excellent - thanks Vito

I don't have the drains you mention and thanks for reminding me to trip the breaker - I always seem to forget that.

Sounds easy and straightforward. This time I won't over-tighten the bolts but after 20 years I'm sure replacing is a good idea. Btw, I found the gaskets even cheaper from a Canadian on Amazon that I've bought from before. They were $50 CAD for 2 but I signed up for one of those Amazon credit cards and they gave me a $15 rebate that I used on the gaskets! Cheap is as cheap does

Jim J - I'll take some pics when I do it and post them up

Old Scout · 11-17-2020, 07:09 PM

….14 by 14 inch is std gasket size....gaskets are generic--cheaper gaskets are open-cell foam while the better quality are closed-cell and more substantial [ie, wont crush as much]....if you have drain cups, doubling the gaskets is better....don't unhook the unit's wiring connections, just separate and re-glue/seal the gaskets at the corner....I prefer to use a bit of sealant between gasket and roof surface to get a better seal...use hard rubber blocks of appropriate thickness on 4 corners of unit that will support the unit on the roof, yet allow gaskets to compress a bit....tighten the 4 bolts back down--like 50 or 60 inch/lbs.....don't try to make this too difficult--its not...

JerryLook · 11-17-2020, 09:45 PM

Good info in this thread. Thanks guys.

Old Scout · 11-18-2020, 06:46 AM

….good catch--depending on brand of rig, the ducting will have to be disconnected and then resealed...

IC2 · 11-18-2020, 07:14 AM

In my 2nd a/c's Dometic installation booklet they advise that you retorque the a/c down after a while.

On the existing unit I pulled the inside cover off and found that the 4 mounting bolts were nowhere near the recommended tightening figure of 40-50 in lb (compress the gasket about .50"). They were just finger tight after 2 years use.

I also found that 40-50 in lb didn't do a bit of compression on the new installation gasket (2nd a/c) so snugged the bolts until the gasket compressed the ~1/2" and used 100 in lb.

This is a sample Dometic installation manual :https://www.manualslib.com/manual/15...?page=8#manual

Old Scout · 11-18-2020, 03:56 PM

….my opinion, but with the units weighing in at nearly/in excess of 100lbs....without rubber block outriggers on the roof, the unit will eventually crush the foam gaskets as your rig goes bouncing down the road--regardless of how much you decide to torque the 4 hold-down bolts.....at best, you will have to check/ "re-torque" the 4 bolts periodically.....