I'm tracking down the hisses in my hvac system. It occurred to me that the hisses may not be the result of the hvac control, but may be elsewhere in the system. My worst hiss seems to occur when I go from no heat to some heat with the bottom slider. I found the vacuum diagram here:
https://www.thirdgen.org/forums/atta...umcircuits.jpg
That however is incomplete. Just before the violet hose enters the A/C control head it splits and goes to another control on the back driver's side of the unit. Also going into this is a grey vacuum hose. This split, and the grey line do not appear in any of the vacuum diagrams I can find. Interestingly, when I disconnect them both the grey, and of course violet lines have vacuum.
1) Why would there be a selector that connects two lines which already have vacuum?
2) What does the gray line do?

 

I think this is the diagram you are looking for.

 

Jermdm-
That's exactly what I'm after thank you. That isn't by chance out of a Haynes manual is it (In which case I just missed it in mine)?
Where is the "Heater water valve vacuum motor"?
I know where the controls fed by the blue, red, brown, and orange lines are but I've never seen the grey one.

Thank you

Edit for future reference:
The orange line goes to a vacuum actuator which can be found by removing the panel above the passenger's feet
The blue and brown(ish) lines go to actuators which are to the right of the driver's feet. I assume there should be a plastic cover there but my car doesn't have one there.
The red line goes to an actuator along the mid line of the car behind the hvac control but all the way forwards against the firewall. I got to mine via the driver's foot compartment. You need to depress the brake pedal and put your head there to see it.
The violet line is the vacuum supply line and comes from a black less flexible vacuum line through the firewall.
I'll post here about the actuator the grey line is attached to just as soon as I find out where it is.

 

I just had another realization. Since I have no A/C, does this valve really do anything for me? Can I simply plug the gray and second violet line? Will it make the interior of my car much warmer for the passenger's feet than it needs to be?

 

I think the heater water valve vacuum motor is the black valve under the hood attached to the heater hoses on the pass. side of the motor. It allows hot coolant to enter the heater core when you use the heater. The diagram is from my chiltons manual. Glad I could help.

 

Apparently more was screwed up than I thought. I couldn't find the vacuum actuator but I did find the hose on the engine side of the firewall. It plugs back into the vacuum line off of the intake. I guess it's always on in this case, which is fine as my A/C doesn't work anyways. I ended up plugging the lines to the little dial as the air temp is controlled by a cable and not by the vacuum lines. At some point in the future I might try to track it down further but right now I can't see much between the engine and the firewall. I suspect the controller may have been removed by the previous owner when he swapped the engine.

If anyone (probably someone in the middle of an engine swap) could post a picture of the vacuum actuator in the engine bay for future reference when people see this thread in the future that would be great. I can't as my car doesn't seem to have the part I was looking for.