mwilkinson Posted March 15, 2021 Share Posted March 15, 2021 Hi Guys, I'm currently rebuilding my HVAC. Other than being very dirty I want to address all the perished foam on the blend valves. I've totally dismantled the unit and all the blend valves need new foam. The old foam is FUBAR and smelly. I'm trying to work out what foam to use. I suspect it needs to be a closed cell foam (non water retaining) that is heat resistant. I'm not sure any off the shelf adhesive backed foam will work as the adhesive is never that good. Has anyone done this? 1 Quote Link to comment Share on other sites More sharing options...
rider Posted March 15, 2021 Share Posted March 15, 2021 I've replaced lots of foam in classic car refurb of heater boxes. There are lots of ads on eBay for the kind of foam that'll sort out your needs. All you needs is a pair of scissors or craft knife and some contact adhesive spray. Hopefully the old stuff is old enough to just peel off without leaving adhesive blobs behind that are a pain but a bit of heat usually softens those up. I had such fun replacing all the foam on my Mustang heater when I changed the core. https://www.ebay.co.uk/itm/3-x-A4-size-medium-density-sticky-foam-car-heaters-draughts-vibration-DIY-crafts/202699821088?hash=item2f31d9d020:g:CSEAAOSw7Mtc-Nhn https://www.ebay.co.uk/itm/Master-Space-Heater-Input-Foam-Genuine-Filters-Diesel-Compressor-Paraffin/324347846864?hash=item4b84a360d0:g:sakAAOSwHVVflWfw Quote Link to comment Share on other sites More sharing options...
mwilkinson Posted March 16, 2021 Author Share Posted March 16, 2021 Have you used the adhesive backed foam or did you buy sheet foam and a separate contact adhesive? I note that the foam density also varies between the different blend valves. The ones closest to the heater matrix are a low density open cell foam, where as the ones further away appear to be a high density closed cell foam. I assume this was done for a specific reason? Quote Link to comment Share on other sites More sharing options...
j_jza80 Posted March 16, 2021 Share Posted March 16, 2021 3 hours ago, mwilkinson said: The ones closest to the heater matrix are a low density open cell foam, where as the ones further away appear to be a high density closed cell foam. I assume this was done for a specific reason? Condensation, most likely. Quote Link to comment Share on other sites More sharing options...
rider Posted March 16, 2021 Share Posted March 16, 2021 I've only ever seen or used spray contact adhesive with foam. It covers fast and quick then tack dries on the surface without being absorbed into the foam structure. Denser foam is usually for sound reduction so maybe you'll find that the denser foam pads are the ones closest to the fan or air outlet? You see on places like eBay a lot of options for dense foams with PC's presumably to act as sound insulation on towers. You could always ask the foam density with suppliers to see what ranges are out there readily available. You'll probably have to teach most of the sellers how to measure density but that would be one approach you could use. Quote Link to comment Share on other sites More sharing options...
mwilkinson Posted March 16, 2021 Author Share Posted March 16, 2021 Thanks guys. I trawled eBay and bought a range of foam sheets and tapes. I'll see what arrives and if I can compare it to the stuff that is currently there. I've also ordered some 3M 90 adhesive spray. Quote Link to comment Share on other sites More sharing options...
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