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I used exactly what you did but the foam on the doors just falls right off. Maybe it was an old batch that lost its stickiness.
Oh are you talking about the flaps/vent valves on the unit? I was thinking the car doors, for some reason, lol.
They weren't as sticky as I would have liked, but they held on okay on the metal flaps. If I remember correctly they didn't stick as well to the plastic ones. I ended up using, I think, JB weld to secure it.
I should have mentioned this earlier but if I were to do it again, I wouldn't use that same stuff for the flaps. It's a bit too hard and dense for the application as well. I'd try to find something a little softer and stickier. If your unit is still apart, try something else.
Sorry for the bump but I would like to confirm the thickness of the foam used. I found that the 5/32" natural gum foam was the best thickness and material I found. I tried about $150 in other foams and they were all too thick or too stiff or too thin to work properly without causing undue stress on the motors.
One 10' x 4"(93625K184) and one 10' x 6" x 5/32" (93625K194)are plenty(softest avail). For the molding 1/2 x 1/4" (8709K42) thick strip of 10ft works well(won't be gum). Go for the softest that mcmaster carr has.
To remove the old foam, lacquer thinner works INCREDIBLY well. It removed everything and didn't damage the metal or plastic. After everything has dried I highly suggest using a thick tacky gel adhesive to get the foam to stick to the plastic pieces. They are not smooth and the adhesive backing doesn't stick too well to the plastic. For the metal it's fine.
Hello Fellow FD HVAC Rebuilders!
I recently followed this thread to help assist me in picking the correct foam for the blend doors that don't cost an arm and leg. I purchased all of the materials from McMaster, even some extra for comparison.
PN: 8709K42, 1/2" Wide x 1/4" Thick x 50ft Roll (For Mating Surfaces)
PN: 8614K81, 54" Wide x 1/8" Thick x 1ft Adhesive Backed (For Covering Wire Harness)
PN: 85175K23, 54" Wide x 3/16" Thick x 1ft (For Blend Doors)
The original poster and many others used PN: 93625K194 6" Wide x 5/32" Thick x 10ft Adhesive Backed Gun Rubber Foam, but most complained about it being too stiff but right around the correct thickness, I purchased both for comparison and for the following reasons I picked the 85175K23 foam instead. It is a softer foam to compress easier to create a tight seal, it is also oil-resistant and my biggest plus is being flame-retardant! The only down side is that it is not adhesive backed so they will need to be glued down using some kind of polyurethane type glue, although the original poster did mention that they had to adhere down the adhesive backed pieces anyway as it wouldn't stick well to begin with.
For an adhesive recommendation I would likely say try something similar to a contact adhesive like woodweld contact cement (I believe is also what the original poster used), I tried using E6000 and it works well once stuck down but the application process for it is less than ideal for the semi large surface area the blend doors have.
Hoping this can help someone in the future be more confident in their material purchases when tackling the job! In the process of doing my main heater box now!
Last edited by Manderspeed; Feb 18, 2026 at 04:23 PM.
Reason: Corrected Typo
