Heater/AC Vacuum switch layout


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Sep 2, 2023
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Hey friends,

This is my 2nd thread about my efforts to troubleshoot my heater on my '65 Imperial Crown. I ended up having to swap out my switch because the nipples where the vacuum lines connect were broke off. I found a pricey NOS replacement- opened it up to clean and lube anything that needed it ...the push buttons were very stiff. I was trying to be careful and not spill out the 4 thin funky shaped files inside that slide from side to side when you push in the buttons. I accidentally dropped the switch and the files came out. I looked into my old broke switch to see the order in which those files should go in and copied what I saw to put mine back in. My old switch did not work right so I'm uncertain that copying the order from that was right or wrong. My question now is, what is the proper order they go back in?

I've attached a drawing and tracing PDF of the 4 files and the order I stacked them in the switch. Please confirm if I've put them in right or wrong before a put it all back in the dash.

Last of all, regarding the vacuum lines - how can I test if those are operating correctly? For example the button marked "Fresh Cool" , if I push that, shouldn't that open up the large fresh air door on the firewall, just below the cowl? If so would I just key on and push that button and the fresh air door open, or do I need to start up the car and let vacuum build up first? This is all new to me so forgive my ignorance.. I just need to be sure how to properly test everything connected to the Heater/AC switch when I get it put back. Thanks


  • Heater switch.pdf
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I am not sure on your selector plates. But for vacuum testing with car off, I use a mighty vac to test all my lines. I also have an electric vacuum pump that I can leave running and adjust the amount of vacuum I draw. You can see how much vacuum is needed to move an item by watching the gauge as you create vacuum

Thanks for the info gents ...I'll take a dive into it
Update: Okay I think I have it all working w/ the replacement Heater switch. One thing about my controls that seem different than the manual, is my fan setting and temp setting controls. The manual says for hotter air move the slider control towards the "WARM" word, which would be towards the driver side of the car. Well mine is opposite; The air gets warmer as I move away from the WARM ...but it never gets really Hot, so I'm not sure if the cable is oping the door all the way. My experience w/ old cars is that they should easily blow some HOT air.
My fan control has 3 positions Low/High/Med. The manual says the High should be furthest position right ( mine is center position ), Medium is center position ( mine is right ) ..and Low is position left ( same on mine ). So I don't know why my High and medium are swapped.

Lat of all I wanted to know about the operation of the system. For example when I engage the HEAT the lower vents on the floor, and the fresh air vent door on the firewall both close up. should they do that when I engage the HEAT? Yes? Also when I turn the system off, those same doors open back up, and being open seems to be their default position ...is this right? Defrost does direct the air to the upper vents strongly when I select that, so I think that's good. I don't have my A/C working yet so I dont push that button. But from what I can tell the controls are making things respond ...correctly I hope.

BTW: the lower vents, ( not the floor vents ) don't seem to have any air flowing out, or at least very little ... I've checked the ducts and they are connected ... so what could I be missing or do these not blow out strong?
I’m glad you have made progress. It almost sounds like you have the switches installed upside down!?!

All I can offer is to double check with the shop manual for your car.
I’m glad you have made progress. It almost sounds like you have the switches installed upside down!?!

All I can offer is to double check with the shop manual for your car.
Okay so I took some video ( my apologies in advance for the quality ) of me operating the A/C-Heater controls on my 1965 Imperial to show and explain to you what it does. I hope some learned fellow on here can answer questions I pose in the video, and confirm that Yes my system is working correctly, or NO it ain't. Video links at the URLs below ....I hope you see them, not sure if it's letting me post the video

video 1: www.flickr.com/photos/25722625@N06/53546392303/in/album-72177720314990030/
video 2: www.flickr.com/photos/25722625@N06/53546640030/in/album-72177720314990030/
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Might try contacting this guy: Mopar Vacuum Switch Restoration Contact: Anthony Powell,
Phone: nine zero three, eight nine three, five six seven four.
E-mail: aepowell66@gmail.com
1305 North Grant Drive, Sherman, TX 75092

He rebuilt one for me for a '64 Sport Fury years ago. Worked perfectly, very knowledgeable.