Hey all,

So I'm trying to track down a stalling issue and trying to trace out a vacuum leak. I noticed that no matter how hot the car gets the THERMAC valve never opens. If you unhook the vaccum line it pops open and the previous owner had just removed the heat pipe from the engine so that it always pulled in hot air.

I suspected that the temp sensor was bad in the air cleaner due to it's very poor condition and the previous owner just never bothered to fix, but even after replacing it the problem persists. I'm now wondering if the previous owner got the vaccum hoses reversed.

I cannot find a diagram online that specifies which hose connects to which port on the temp sensor so I wanted to ask here.

The temp sensor has 2 ports, a wide open mouth port and a narrow mouth port. Just to confirm which one does the THERMAC air cleaner valve hook too and which is connected to the vacuum line from the car.

Did you find which line goes where on the temp sensor?

the temp sensor vacuum control valve in the air cleaner is used to keep the air temp around 110F.. so if it is causing the air to be too cold you will get hesitations and perhaps stalling when the air temps drop below 60F approx.. reverse the hoses on the sensor see if it works ..

also if it is cold out like 30F the temp door will stay in the exhaust manifold position. also I used fiberglass insulation around that hot air pipe set on the manifold so it will hold more heat to the air cleaner when very cold temps hit.. had this set up for all the time since 1984.. reason I did this decades ago it I had these issues on 1960's/1970's GM sedans with this type setup..

possible you have the ability to use a heat gun air cleaner cover off . have a temp sensor to measure the temp at the sensor .. blow the heat on the sensor see if the door moves when its around 110F. then if not moving reverse the hoses.. then try to adjust the sensor it is adjustable ..

also you can buy another new one or perhaps go to scrap yard and see how its connected and use the scrap yard part.

Old thread that never had resolution.

Does anyone one which side is the vacuum source and which side goes to the THERMAC valve?

TIA,

-CB

Doesn't matter. It's like a ball valve you can go look at, at HD or something. Go LOOK AT one and don't bother telling me you "just have to know" until you LOOK. GO LOOK. Handle one way, it's a blockage; handle the other way, it's a piece of pipe. Doesn't matter which way is pressure or load. The temp vac valve in the air cleaner is EXACTLY the same way. It's just a gate. Nothing more complicated than that. It either opens or closes.

Hook up the vac lines whichever way they lay neater. Odds are, that'll be the way the factory did it, too.