Fixing up an 86 trans am with the 305 TPI engine. I know the mode-selector for the HVAC controls is powered by vacuum that comes off the engine, and has to run through the firewall somewhere. On my car the vacuum hose is disconnected on the engine side and I can't for the life of me find where to re-connect it at the firewall. Does anyone know where the actual connector is that you plug the engine-side vacuum source for the HVAC system is? Any pictures or descriptions would help.

I hope it's clear what I'm describing. Where to connect the hose that comes off the back of the air intake block, through the firewall, to supply vacuum to the HVAC heater box. I don't know where the connection at the firewall is from the engine side.

 

The vac line for the HVAC is in the HVAC wiring harness, which passes through the firewall right by the heater hose fittings. It doesn't go straight to the engine; instead it connects to probably a check valve and/or a T, the other leg of which goes to a vacuum reservoir.

 

Oh awesome! I know where that is, I saw a little vacuum line coming out of a wiring harness right next to the blower motor, so that must be it. It was disconnected, and I couldn't tell what it was for.