RE: [Chrysler300] 1964 300k
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RE: [Chrysler300] 1964 300k



The first thing to do is check the system as-is to see which (or all) motors are not working.  Document your findings in your notes.  inspect all hoses for being connected and not split or broken off—especially the source hose which may be attached to a fitting at the back of the intake manifold.  Your Performance gauge on your console will give you an indication of whether you have good vacuum at idle.  If punching the push buttons on the controller changes that vacuum at steady idle, this could indicate a vacuum leak somewhere in the system.


You can then test each actuator/motor/servo by VERY CAREFULLY removing the rubber connector from the back of the HVAC control panel and testing each side of each actuator with a hand-held vacuum pump or any other vacuum source (including an idling engine with the car outside for safety).  The reason to be careful is that there are seven tiny plastic nipples on the back of the HVAC control panel and the single rubber connector will want to stick to the nipples and be difficult to remove without breaking a nipple.  If you find one or more nipples broken already, they can be repaired.


One of the seven hoses fastened to the connector is the vacuum source for all the motors.  The other six are connected in pairs to the three motors—one to “Open” the door and the other to “Close” the door.  Our service manuals have details of which hose goes to each side of each motor.  They are color coded.  If the vacuum test shows one or more door to be functional under test but not working by the push buttons the problem may be in the controller body.  There are sliding plates within the controller body that are positioned by the push buttons and direct vacuum to the doors as is appropriate.  They also control the A/C clutch and power to the fan-speed switch.  I had my controller rebuilt while I had it out.  The old plates were lubricated with a grease that had become stiff over the years and were replaced with new plates made of modern plastic.  


I have attached two pictures of the back of the HVAC control panel—showing the seven vacuum connections. See: Pages 1-6 through 1-8 <>  for some detail on the servo’s.  Bob Merritt has several excellent You-Tube videos showing the HVAC system including:    &          


Rich Barber

Brentwood, CA


From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of Harry Torgeson torg66@xxxxxxxxx [Chrysler300]
Sent: Saturday, December 03, 2016 2:31 PM
To: Chrysler 300 List <Chrysler300@xxxxxxxxxxxxxxx>
Subject: [Chrysler300] 1964 300k



My shop that's done my all my work does not want to fix my vacuum controls, so I might try it my self, they said the vacuum servos are frozen not working,  does that mean the diaphragms are perforated? How would I test this,  car had been siting  in a museum  for 12 years prior to me getting it. I have seen the video in the news letter about removing the whole unit, hope I do not have to, if I need servos where would I get them? Thanks for any Ideas.

Thanks Harry    

[Non-text portions of this message have been removed]

Posted by: "Rich Barber" <c300@xxxxxxx>

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