Vacuum pot/actuator/canister for HVAC doors

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MopaR&D

MopaR&D

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The vacuum pot that actuates the air-recirculating door on my '72 Dodge truck is going out (has a hard time returning the door to closed position), anyone know where to find a replacement? Or if there is a way to "repair" it? I'm guessing the diaphragm inside has a small tear or leak of some sort. Or does the rubber grommet the rod passes through also act as a vacuum seal for that side? I might try putting some grease on the rod and see if that frees it up but I've tried to find these vacuum pots before and never had any luck. It is the dual-acting type with a vacuum line going to each side.

I think my '70 Duster needs one too now that I think about it, pretty sure the one that switches from dash vents to windshield/floor vents is "sticky" too. Have to reach under the dash and manually move the rod.
 
This is the guy, canister-looking thing

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Have you googled them? Or just called around? I remember when drove my buddys 71 Cuda up to go to the Garlits show his stuck. To get heat we had to manually open it
 
I've broken two blend door cables in the past and in both cases found the foam on it had deteriorated and in the heat of summer the adhesive glued the doors shut.
Could be that the canister is OK, but something is causing the door to not want to move.
Usually, not always, those canisters just 'pop' and fail to work. Easy test is with a hand pump to see if it holds position. If it retracts, then slowly moves back - it's got a leak and is bad. If it doesn't, then something else might be causing drag. If the door isn't returning to rest, the spring inside the can could be worn and a 'helper' spring might work, or again there's just drag on the door from debris or rust on the pivot shaft. I'd try squirting a drop of motor oil onto the blend door shaft to see if it helps - assuming it can be reached.
 
I pulled apart the heater box to replace the heater core last winter and I know the door isn't binding up. I have a strong feeling it's the rubber grommet that seals the rod to the canister because it works perfectly pulling the door to the open position but has some trouble pulling it closed (pushing the rod out of the canister) and I can hear an occasional "hissing" sound although the vacuum lines are good. I'm gonna try slathering some o-ring grease on the rod (I feel dirty typing that lmao) and see if that does the trick, it's not quite broken enough to be broken lol.
 
MopaR&D said:
I pulled apart the heater box to replace the heater core last winter and I know the door isn't binding up. I have a strong feeling it's the rubber grommet that seals the rod to the canister because it works perfectly pulling the door to the open position but has some trouble pulling it closed (pushing the rod out of the canister) and I can hear an occasional "hissing" sound although the vacuum lines are good. I'm gonna try slathering some o-ring grease on the rod (I feel dirty typing that lmao) and see if that does the trick, it's not quite broken enough to be broken lol.
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The hissing is kind of normal when vacuum is released. Air hissed into the can, but air also escapes around the rod too. I could see a stiff/hard wiper or diaphragm causing drag.
Old rubber-band-powered airplane guys used to soak their rubberbands in simple green for a few minutes. Apparently it worked well to 'revitalize' the rubber to some extent. Haven't done a bunch of it myself, but it's worked when I've tried it. Following up with o-ring grease should help too.
Another suggestion I've run across is to use Honda silicone grease (Honda Genuine 08798-9013 Silicone Grease) for hardened rubber. I bought a tube last year, but haven't gotten around to using it - but lots of detailers swear by it.
 
Phreakish said:
The hissing is kind of normal when vacuum is released. Air hissed into the can, but air also escapes around the rod too. I could see a stiff/hard wiper or diaphragm causing drag.
Old rubber-band-powered airplane guys used to soak their rubberbands in simple green for a few minutes. Apparently it worked well to 'revitalize' the rubber to some extent. Haven't done a bunch of it myself, but it's worked when I've tried it. Following up with o-ring grease should help too.
Another suggestion I've run across is to use Honda silicone grease (Honda Genuine 08798-9013 Silicone Grease) for hardened rubber. I bought a tube last year, but haven't gotten around to using it - but lots of detailers swear by it.
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A while back I got a tube of Parker Seals brand O-ring lubricant which works wonders sealing and lubing rubber parts. If that doesn't work I'll see about carefully removing the grommet/wiper and try the Simple Green trick. I actually just found a YouTube video on using Simple Green to restore rubber parts, I'll watch it after I get home from work.
 
So the grease helped but I noticed the rod is over-extending because the seals going around the recirc door and the hole in the fender are gone so the door moves farther than it's supposed to in the closed position. I can see the door through the recirc vent under the dash but can't reach it unless I take the heater box apart again (not fun) or cut out the recirc vent "grille" all the way around but then I'd need to figure out a way to reattach it when done and it's all that old-school black plastic. I might try at first to just JB-Weld a small metal tab onto the door to act as a stop but it really ought to be sealed, it leaks air in to the cab when driving down the road and you can feel the air coming out of the vents. If/when I move to Texas I'll need to go through it all again anyway because I'm gonna need to install A/C if I want to drive the truck more than a few months out of the year lol. Truck originally came with A/C so the heater box is set up for it but that recirc door leaks too much for my liking.
 
I don't know of any fix for them, unless you can straighten the lip out and get to the diaphragm. However, they are called a vacuum servo. That might assist you in finding another one. I'm decent at findin stuff. I'll search too and see if I can help.
 
RustyRatRod said:
I don't know of any fix for them, unless you can straighten the lip out and get to the diaphragm. However, they are called a vacuum servo. That might assist you in finding another one. I'm decent at findin stuff. I'll search too and see if I can help.
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I appreciate that. It seems to be working decently now after I cleaned and greased the actuator rod but it would still be nice to know where to get those things. Right now the bigger issue is getting that door to close and seal properly in the right position.
 
MopaR&D said:
I appreciate that. It seems to be working decently now after I cleaned and greased the actuator rod but it would still be nice to know where to get those things. Right now the bigger issue is getting that door to close and seal properly in the right position.
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Cool. Maybe that's all it needed. So far, I've had zero luck. I'm still lookin though. I tell you who might have one. Formerly Frank Mitchell (RIP) Mopar parts, it's now AMS NOS Parts. AMS Obsolete Home Page People often bitched about Franks high prices, but he really had the stuff. They boast over a million NOS Mopar parts. Maybe if you can get a part number off it, they can help. I think they have a parts lookup too though.
 
Test the diaphragm with a hand vacuum pump. If you measure a leak, before faulting the car vac pod, first verify your vac pump and hose by plugging off just the hose to see if that holds vacuum. If you get desperate, my 1985 M-B 300D uses vacuum pods in the climate box, and you can still find those in junkyards, plus likely later cars still had that. The pods are red plastic and you likely would need to mod the rods to match, plus the mounting bracket.
 
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