mtnmanut

im new to this forum,so hopefully one of you vette experts can help. i have a bone stock 84.i have no vacumn to the heater ac controls,in searching for the vacumn source,i found one connection at the motor.it tees off from the vacumn line that comes off the manifold and goes to the cannister.that little black plastic line goes into a wiring harness appr. behind the dist. from that point it gets impossible to trace.is this the source for the hvac.its nearly impossible to trace from under the dash,and i have been unable to find a vaumn line diagrahm for under the dash.please any help.thanks in advance

383vett

Yes, that is the sole source of vacuum for the hvac controller. There is a conical 1 way valve that tees off from the manifold. One goes to the round vacuum reservoir by the left headlight, and the other goes into the firewall to the vacuum controller. A factory service manual will help you trace the vacuum line in detail once it disappears into the firewall. Maybe another forum member can come up with the diagram. Good luck. Willie

Mtn Billy

There are drawing in the FSM, but none that show the routing. This was driving me crazy also till I figured out that it goes thru the firewall with wiring. The vacuum feed goes from the intake manifold just in front of the vacuum canister line. From there it goes to the AC pump then back thru the firewall to the vacuum selector on the back of the heat/AC controls.

My problem was a collapsed main feed just before the HACV controls. I made a presumption that because I have vacuum the problem was somewhere else. It wasn't! The vacuum should be about 30 inches, I had nine. The feed had a collapsed line at the tee where it splits off to the hot water and the vacuum selector switch.

Check vacuum at:
intake manifold
then AC pump
then vacuum switch

I have drawings of this stuff but can't include them.

Happy hunting
Bill

mtnmanut

thanks for your replies and assist,you say it goes to the ac pump? DO YOU MEAN THE SMOG PUMP OR AC COMPRESSOR i have heard some call the smog pump a air control pump. and when you say vacumn switch is that the switch on the ac heater controls at the dash.god i'm a idiot. thanks. i'll look when i get home. be a few days on a bus. trip

Mtn Billy

Oops, on the AC compressor. Try this url http://ww2.justanswer.com/uploads/Da...ram_htrac1.jpg