61 AC and Heat problem

[pauls61cad]

My problem is while the AC is operating the heat is also operating. The heater control operates correctly without the AC on, but when I turn the heat off and turn the AC on the heat also blows through the heating vents. The AC vents just blow cold air as they should. Can anyone help me? Thank You. Paul Perreca. I forgot to mention I have a 1961 Cadillac.

[Thomas R. Murray III]

Paul, Call a gentleman by the name of Joe Zampini of A-Z Radiator located in Trenton, NJ (609) 394-3722 / (609) 394-1629. He has been dealing with AC systems for over 40 years and cut his teeth on the early Cad AC and climate control systems of late 50's and early 60's. I have never brought him a problem that he was not able to resolve. Tell him I gave you his number and he'll set you straight. I can't wait to see the '61 when she is done. - Tom
p.s. Happy Thanksgiving to you and your family. I didn't forget about the headlamp switch

[dplotkin]

One of your vacuum operated air door diaphragms is not operating either because it is mechanically stuck, ruptured, or is not receiving its vacuum signal from its source. Unless someone else chimes in with a direct place to start, I would first look for any disconnected vacuum lines running to the 4 various vacuum operators and to the dash controls. Beyond that it is a matter of pulling out the shop manual to learn which operator positions which air valve and when. With that info and a borrowed hand operated vacuum pump you can test each unit, and find out what has failed. If you are lucky, you will find a leaking piece of line.

Dan

[Dan LeBlanc]

Sounds like the vaccum actuator for the heater door is stuck open allowing air to flow through the heater core.  That one is best accessed from underneath the car as it is under the a/c box.

Had to change that one on my 61 Fleetwood. 

You may need to remove that box as it may be seized open.