Hello all, restoring a 92 rs 305 and after tearing the poor thing in half I finally discoverd why my ac heating servos wouldnt change vents, and how they worked, after some research ive discovered that a vacuume line that sits behin my intake (tbi, i had always wondered what it was for) goes to that vacuum system. My question is, where does it connect? The hose is plugged (with a stick, compliments of previous owner) for the time being and ive looked around the blower motor housing and what not, but i just cant find where it connects...please help?

I correct myself! Ok ive now discovered that the plugged vacuum source behind the intake...is still a mistery, wha is it? and the ac heating control vacuum hoses lead to two main vacuum lines, one to the heater water valve ad the other...to what? Is anyone out there who can please help??

My problem, airflow is stuck on defrost and my ac heating vent doors arent getting vacuum to open and close to redirect air flow, my dash is taken apart and im as close to the firewall as i can get

Do you have any pictures that might help identify what you are talking about? My dash on my TPI engine is doing the same thing (won't switch vents), but I haven't gotten a chance to tear it down and look around yet. I do have a 91 firebird service manual though that might be similar to your car if I can see what you're talking about.

Under the hood, the system should look like this:

A line plugs onto a nipple on the intake manifold, behind the TBI if memory serves. Further downstream in that line there is a check valve, pointed such that vacuum only can go one way; that is, the engine can suck air into itself through it, but it won't let something on the far side, suck on the engine. beyond that, there should be a T. One leg of the T goes to a vacuum reservoir, whose job is to hold enough vacuum so that when engine vacuum goes away (when you floor it for example) there's still some in there to hold the servos in place, and the check valve keeps the vacuum in the reservoir from escaping back into the intake manifold. The other leg goes to the A/C control head, via the line that goes through the firewall.

Your reservoir is probably The Orb Of Power, about a 4" dia black sphere with one vacuum fitting, in one of the fender wells. I think it's in the driver's side one, visible from below, under where the battery would be if it was on that side instead of where it is.

Once you find the Orb, or if it's missing you get one from the junkyard, you can build all this with stuff hanging on cards at yerbasic corner parts store or even places like AZ.

TPI obviously gets the vacuum from a fitting on the plenum instead of behind the TBI, AFAIK the Camaro & Firebird systems aren't too terribly different, the manual for the one should inform you at least somewhat about the other.

Yes yes it's all there and I connected them and it all works! I can control my vents now your a genius thank you kind sir!!