Diagram for A/C vacuum lines

[Mike231]

HELP! I fixed the vac line going to the distribution block and my a/c was working, dash vents, floor, etc. A few days later it went back to floor only. I have/ can hold vacuum on the line going to distro block. When I take the line that's going from the vac box on pass side down into the fender that line won't hold a vacuum.
Does anyone have a diagram showing where this goes, and the whole system too?
A/C works great as far as being cold. New compressor and cleaned out condenser. R-12 does work great in this system.

[Steve Wood]

https://www.vortexbuicks-etc.com/AC_Heater_Vacuum_Lines.htm

[Mike231]

Thank you Steve. I couldn’t find it.

[Steve Wood]

Not sure what you mean.  The distribution line is fed by one of the small plastic lines that run across the firewall under the hood.  One of the small lines feed the heater valve and the other one goes down into the firewall and into the passenger compartment.

The small plastic line connects to the two way check valve mounted on the firewall  on the drivers side.  The other side goes to the vacuum reservoir ball under the fender and the the inlet goes back to the vacuum block pipes on the plenum.  If there is any leak in the hose going to the two way valve on the firewall, or the line going to the storage ball, then you won't have vacuum to operate the AC controls

[Steve Wood]

I would attach my vacuum gun to the line coming off the 2 way check valve on the firewall and see if you can pump up a vacuum on the small plastic line and if you can does that make the ac controls work?

You may be losing your vacuum thru the control head valve   https://vortexbuicks-etc.com/acvacuumswitch.htm