AC/Heat Vacuum line ?

[70GMCer]

My 83 has factory ac that I'm going to try & piece back together.

On the round, black vacuum canister that is located above the blower motor, (engine bay) there are 2 vacuum tube connections. One larger than the other.

Which one goes to the inside to the control panel & which one goes to the vacuum switch on the engine manifold?

I'm going to take a guess & say that the larger connection goes to the vacuum switch on the engine. Is this correct?

Also, I believe one connection has a built in check valve.

[cruizin01]

I pretty sure you dont use both connections. You'll just 'T' the connection closer to the engine. Im pretty sure you use the connection that has the little shroud around it.

edit. found this picture for ya.

[70GMCer]

Originally Posted by cruizin01

I pretty sure you dont use both connections. You'll just 'T' the connection closer to the engine. Im pretty sure you use the connection that has the little shroud around it.

edit. found this picture for ya.

That pic is not the one I'm talking about.....

Here's a pic of the one in my truck

[Dead Parrot]

On my 75, the large hose goes to the intake manifold, the little one goes inside the cab. Any check valve must be in the vacuum reservoir. There must be one somewhere as I can get a couple vent movements with the engine off.

Mine came with minimal emissions stuff so no switch, just a run straight to the manifold.

[70GMCer]

Originally Posted by dead parrot

on my 75, the large hose goes to the intake manifold, the little one goes inside the cab. Any check valve must be in the vacuum reservoir. There must be one somewhere as i can get a couple vent movements with the engine off.

Mine came with minimal emissions stuff so no switch, just a run straight to the manifold.

thanks.....