Re: [Chrysler300] Servo
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Re: [Chrysler300] Servo

I should have added that JY Chouinard found an excellent explanation of vacuum tube routing and function ( impossible to find in FSM') in I think 59 Imperial FSM , he uploaded that with very valuable added info I think via Bob Merrit to site tech info . I have no experience with 59 cars but am told they use this system , first year . If you note in the referenced later FSM 's , nothing at all in there about the vacuum system logic . JY 's diagram ID each port correlated with which button is in and hose stripe colors . 

Sent from my iPhone

On Nov 19, 2016, at 3:01 AM, 'Rich Barber' c300@xxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

Hi, Harry:


O&M instructions for the air distribution controls system are found in the service manual on pages 24-23 to 24-25.        The three dampers or baffles are called “doors” and are opened and closed by vacuum.  The vacuum distribution system center is a white plastic block on the back of the heater-A/C control module.  (Fig. 28-control switch).  Pushing each of the five control buttons switches the vacuum to one side or the other of the diaphragm in the three metal vacuum chambers that actuate the doors.  There are seven rubber hoses bound together in a connector that plugs on to the back of the white plastic control switch.  One of the hoses is connected to engine vacuum and the other six hoses go to each side of the three actuator cans.  One to open and another to close that door.  The white plastic control box has seven tiny plastic nipples projecting from its back, over which the seven-hose connector fits.  These nipples are pretty delicate and may have been broken off by a previous mechanic.  If this is happened you might find a real clever way to repair a broken nipple, but you are more likely going to need to go shopping for a replacement control switch.  The white plastic control switch, itself, can be removed and replaced.  Wires to the blower and A/C compressor clutch are also fastened to the control switch and pushing the various buttons will also control the A/C clutch.


With the engine running, pressing each of the five buttons on the HVAC control module should cause the various doors to open and close.  The blower is controlled by pulling out or pushing in the temperature control lever.  With A/C you should have three fan speeds.  If pressing the five buttons does not actuate any of the doors you may have inadequate manifold vacuum or a cracked or disconnected vacuum hose that provides source vacuum to the white control block.  One of the actuators can be viewed by removing the outside cowl fresh air inlet cover.  Another actuator is mounted to outside top of the heater box under the hood and the third is mounted inside and under the dash.  You can view the opening and closing of several of these door actuators fairly easily.


The five buttons on my control module require a pretty stiff push to go all the way in and cause the doors to open and close.  Anyone been successful at lubing these plastic parts for easier & smoother action?  I don’t want to dissolve the plastic block or gum up what I assume are sliding plates inside the block.


Good luck.  Heater-Defrost, at least, season is upon us.


Rich Barber

Brentwood, CA (43F @ midnight—finally had to turn the furnace on--only pushbuttons are on the digital thermostat)



From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of Harry Torgeson torg66@xxxxxxxxx [Chrysler300]
Sent: Friday, November 18, 2016 12:26 PM
To: Chrysler 300 List <Chrysler300@xxxxxxxxxxxxxxx>
Subject: [Chrysler300] Servo



I have a 1964 300K, my sero vacuum system for heater AC does not work, does anyone know how to fix it  and know were its located?



Posted by: John Grady <jkg@xxxxxxxxxxxxxxxxx>

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