No, the "switch" that does that is the servo unit, in conjuntion with the pushbuttons. You need to go to the Unwired Tools website and download the vacuum diagrams they have posted there. They are free for the download, and are very helpful in diagnosing vacuum problems. Your vacuum problem could be the servo itself, any of the 7 vacuum pods in the car, the control panel switch, the vacuum feed from the engine to the heater system, a puncture/blockage of any of the lines, etc... I used a mighty-vac to test everything for leakage, using the Unwired Tools vacuum diagrams, which are functionally equivalent to the ones in the factory manual, but much easier to follow.
http://www.unwiredtools.com/accii.html
The heater system is identical to and copied from one that Chrysler used in 1971. Here's a link to the Chrysler manual for it:
http://imperialclub.com/Repair/Lit/Master/281/cover.htm
Good luck with it!
