Hi everyone!
Can anybody tell me where the vacuum lines for the heater control valve plug into (inside the car.) I have no vacuum at the end that connects to the valve. I also don't hear the hissing noise when I move the selector switch from the A/C over to the Vent/Defrost side. So I'm assuming that I probably don't even have vacuum at the selector switch. What should I look for? I did replace the dashboard in this car not too long ago, so I'm thinking that I probably knocked a line off.
This should finally remedy my A/C problem I've had for awhile. Thanks in advance, Sarge

The only thing I can offer is to look in either an Assembly Instruction Manual for your year or the repair manuals from Chilton's or Haynes.

The vacuum line that supplies the valve on your control on the A/C selector is the only line with no colored stripe. On later years this line either teed off of the large vacuum line to your headlights or came straight off the intake manifold metal tee. This water valve has the same properties as the vent door located in the passengers side cowl that shuts off outside air to the interior. If you have vacuum to that valve and can't find the water control line, tee off the outside air valve line (probably green striped).

Thanks for the info guy's! I really appreciate the help.

Maybe I will have A/C for next year's "hot spell." I couldn't really drive the car that much this year due to the heat. Me and anything over 85 degress with 100% humidity don't get along.
Thanks Again, Sarge

Sarge...just went through much of this in my 78 when I did a heater core replacement. I verified the operation of all systems, tested actuator doors, checked vacuum lines, tracing them all back to source.

The previous contributor had it right...it's the black line that plugs into the back of the A/C selector switch. The shop manual has a nice schematic of how those vacuum lines are run and if I had my scanner up and online, I would send you a pic. The black vacuum line can be traced out through the firewall and than splits back to the port on the intake manifold. The line is more of a tube than a hose as it enters the firewall (looking from the drive's side inside the engine compartment).

Of course, if you've been underneath your dash doing work...there are four different actuators that deliver vacuum to the plenum doors that permits hot and cold air to flow from anyone of those dozen grilles. Your 81 is similar to my 78 and I'm assuming its an air car.

If you have questions...feel free to ask.