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RivNut

Dual Diaphram illustration in '64 Chassis manual

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Earlier this morning I received an email from a forum member asking me about the "Tech Tips" on the Dual Diaphragms that are on a '64 Riviera A/C system.  In particular was his note that the illustration in the factory chassis manual is incorrect.  I had replied that his note had been substantiated by a "Tech Tip" on Chip Little's site.  Here's the info from that site.  At the bottom of the "tip"is the citing of the incorrect illustration.  I've high lighted the Note" that the lines are reversed.  The link to the actual site is also attached.

 

Ed

 

The '64 Riviera A/C system used two identical dual-stage vacuum diaphragms. They are called "dual-stage" diaphragms because there are two "circuits" in each diaphragm. Vacuum applied to either port individually will pull the shaft in halfway. Vacuum applied to both ports will pull the shaft in all the way. You can test the diaphragm by putting a piece of hose on each nipple, sucking on it, and seeing if it holds vacuum. New diaphragms are available from Old Air Products.

 

The upper diaphragm is mounted on top of the heater duct.  It opens and closes the heater air door (not the heater temperature door, which is controlled by a cable).  The lower diaphragm is mounted on the bottom of the blower housing.  It opens and closes the recirculated air door.

It is a PITA to replace the lower diaphragm (the upper is quite easy). If you decide to replace the lower diaphragm:
  • Unplug the wires from the blower motor.
  • Remove the black plastic vacuum tank from the inner fender.
  • Take the heater valve off of the inner fender.  You don't need to disconnect the heater hoses; just move them aside.
  • Remove the blower motor from the housing.
  • Remove the blower housing from the firewall.  This is the annoying part.  Two of the mounting bolts must be accessed from under the car.  I would recommend using a flexi-drive or a universal drive adapter on a socket.
  • Pull the blower housing away from the firewall and turn it so you can get to the diaphragm mounting screws inside the duct.
  • Remove the screw attaching the diaphragm shaft to the air door, then remove the two screws that attach the diaphragm to the blower housing.
  • Reassemble and replace the vacuum hoses.

Don't forget to put a small bead of sealant around the blower box, etc. when you bolt them back to the firewall. 

NOTE: The vacuum diagram in the '64 shop manual (Fig. 11-80) is incorrect. The diaphragms are reversed; the one labeled "Heater & Evaporator Air Door Dual Stage Vacuum Diaphragm" is actually the "Outside & Recirculated Air Door Dual Stage Vacuum Diaphragm" (and vice versa).

 

 

http://www.chip.com/buick/techtips/dual-stage.html

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I'm posting the diagrams that I put together to clarify the various vacuum flows between the various heat and A/C conditions.  You can see from these flows how the two vacuum diaphragms are reversed in the Service Manual drawing. It is important to note that the vacuum switch entitled "Heater Adapter" is physically located on the A/C control head and the "Air Conditioning Adapter" is physically on the Heater control head.  I had installed new hoses based on the color code shown in the original drawing so I will have to make sure the right vacuum motor is engaged by switching them when I install the control heads.  Hope this helps.

1964 Riv Heat-AC Vacuum Flow Conditon-1.jpg

1964 Riv Heat-AC Vacuum Flow Conditon-2.jpg

1964 Riv Heat-AC Vacuum Flow Conditon-3.jpg

1964 Riv Heat-AC Vacuum Flow Conditon-4.jpg

1964 Riv Heat-AC Vacuum Switches.jpg

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58 minutes ago, Bill Lester said:

I'm posting the diagrams that I put together to clarify the various vacuum flows between the various heat and A/C conditions.  You can see from these flows how the two vacuum diaphragms are reversed in the Service Manual drawing. It is important to note that the vacuum switch entitled "Heater Adapter" is physically located on the A/C control head and the "Air Conditioning Adapter" is physically on the Heater control head.  I had installed new hoses based on the color code shown in the original drawing so I will have to make sure the right vacuum motor is engaged by switching them when I install the control heads.  Hope this helps.

1964 Riv Heat-AC Vacuum Flow Conditon-1.jpg

1964 Riv Heat-AC Vacuum Flow Conditon-2.jpg

1964 Riv Heat-AC Vacuum Flow Conditon-3.jpg

1964 Riv Heat-AC Vacuum Flow Conditon-4.jpg

1964 Riv Heat-AC Vacuum Switches.jpg

Bill,

 

Great job.  Can you tell us what each of the three colors you're using represents?

 

Thanks,

Ed

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14 hours ago, Bill Lester said:

I'm posting the diagrams that I put together to clarify the various vacuum flows between the various heat and A/C conditions.  You can see from these flows how the two vacuum diaphragms are reversed in the Service Manual drawing. It is important to note that the vacuum switch entitled "Heater Adapter" is physically located on the A/C control head and the "Air Conditioning Adapter" is physically on the Heater control head.  I had installed new hoses based on the color code shown in the original drawing so I will have to make sure the right vacuum motor is engaged by switching them when I install the control heads.  Hope this helps.

1964 Riv Heat-AC Vacuum Flow Conditon-1.jpg

1964 Riv Heat-AC Vacuum Flow Conditon-2.jpg

1964 Riv Heat-AC Vacuum Flow Conditon-3.jpg

1964 Riv Heat-AC Vacuum Flow Conditon-4.jpg

1964 Riv Heat-AC Vacuum Switches.jpg

Great illustrations but wouldn't it be better if your illustrations hose colors matched your descriptions (red hose colored green, white hose colored yellow, black hose colored white, etc). My two cents worth.

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As far as the colors go, the yellow is source vacuum, the green is anything triggered by the A/C controls, and the orange anything triggered by the heater controls. It’s not totally clear because of the interaction especially when both heat and A/C are on.

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One other note:  The connection to the STV valve is not shown since it is unaffected by this circuit except for a tap into the source line which goes to the large fitting on the modulator valve (mounted on the A/C control head). A blue striped hose goes from the small fitting on the modulator to the STV vacuum port.

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Posted (edited)
4 hours ago, NC1968Riviera said:

Great illustrations but wouldn't it be better if your illustrations hose colors matched your descriptions (red hose colored green, white hose colored yellow, black hose colored white, etc). My two cents worth.

Mike,

 

Bill's illustrations show how the system works. This one shows how it's plumbedIMG_20190710_110554580.thumb.jpg.8e9afd4b43e1e80435e56a6e8822125d.jpg

 

You realize that the hoses themselves are not colored but rather have a trace line in that color on a black hose

s-l300.jpg.c1b63189c3a9fd7ba105bccd0b4919a8.jpg

 

Ed

Edited by RivNut (see edit history)

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