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I have a question about the routing of heater/AC vacuum lines from the cabin to the engine bay. This is for a 76 with AC car. There are three lines that come out of the cabin. One line goes to the exterior vent door, one line goes to the heater hose bypass valve(in the process of replacing this line) and the other goes to the vacuum source(?). On my car this hose(vacuum source) is not connected to anything, just loose. I have looked for an empty T or connection off the other lines and do not see one. I'm sure I am missing something here. Anyone know where this should connect? Thanks in advance!
I just popped the hood open on my 76/ac. I followed the same line down to a vacuum canister. I don’t think the canister is original. Regardless, it is hooked up to a vacuum source as @resdoggie points out.
Thanks for the quick response guys. I am going to take your advice and buy a T this weekend and tap into a vac source line. My only concern was that there would be a source line somewhere that is open. I might try to pick up a vacuum pump for testing. My engine bay is sort of a mess. I'm trying to track down all the gremlins. I'm sure more questions will arise.
Cheers!
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
I just remembered that I had the exact same issue over 30 years ago when I bought my '76. I took the end of the vacuum line and moved it all around the rear of the engine compartment while fully extended. I actually did find the other vacuum hose but I don't remember where it was. Anyway, just follow the vacuum hoses connected to the carb and ensure they are all connected to something. My engine now has only two manifold vacuum lines directly connected to the intake - one dedicated line for the power brake booster and one line with tees for the a/c, lights and map sensor. Nowhere near like stock anymore. Btw, the end of the vacuum line you have can be slipped inside a larger vacuum hose and should seal. Mine has for 30 years.
Last edited by resdoggie; Jun 14, 2021 at 08:24 PM.
Here is what I see missing in the OP 2nd photo.
After the white filter there should be a check valve.
There are 2 ports on the discharge side, one is larger then the other.
The small one goes to the headlight switch the larger of the 2 goes to a Tee.
At the Tee it feeds the vacuum tank front of car and the HVAC vacuum hose.
The Tee has 2 of the same size and one smaller size for the HVAC controls.
My 77
76 vacuum hose question
