Bear with me, I am not 100% on the terminology.

First I had issues with the a/c cutting off when I was accelerating, turns out there was a huge hole in the vacuum canister. Replaced that, easy work.

A/C runs nice and cold, but makes a hissing sound the whole time. If I reach up under the driver's side of the dashboard, there is a servo(I think that's what it is called?) that has a metal rod that goes in and out. It goes in (vents/defrost) just fine, but when it goes to go out (A/C, Max A/C), it gets stuck part the way out, and the hissing starts - but the A/C does kick in. I can pull it out manually all the way, and the hissing stops. But it starts back up again if I've turned the car off and then turned it back on again (say I go into a store or something).

Any ideas here? I completely pulled the dash apart and the glovebox off, and everything on the other side (the servo and door and so on) works just fine.

Perhaps it is a vacuum issue? Maybe not enough vacuum pressure getting to the port on the side of that servo to push it all the way out? Could the check valve(?) where the lines from the canister and manifold meet go bad?

Is there a way to test the vacuum pressure at that end of the vacuum line? What should the pressure be? (I can't seem to find my Haynes manual right now) Should the pressure be consistent throughout the system (say I pull the line that runs in through the firewall and test it at that point, after the valve I just mentioned)?

Thanks for any help. I can't afford to take it to a shop for this seemingly minor annoyance, and I have a feeling it could be an easy fix, if I only knew the answer...

 

I just bought my 2001 Chevy Lumina and it does the same. Great A/C, very cold but it turns on and off.