[3sonsdad]

I realize this is an older post but I was having issues with my 3 port control head vacuum switch so I had to get my vacuum tester hooked up and get this figured out.
My 3 port vacuum switch has part number 7292032-1 cast into the pot metal. These have numbers 1, 2 and 3 cast next to the three ports. Mounted correctly to the air conditioning/ heater sliding control lever assembly under the dash port 1 would be closest to the passenger side, port 2 in the middle and port 3 closest to the driver side.
Port 1 is vacuum in from your vacuum canister under the hood. This has to be vacuum in for this 3 port valve to work correctly.
Port 1 is common with port 2 when the uppermost lever is moved to INSIDE air. In this position vacuum from the vacuum canister draws a vacuum in port 2 and the vacuum line attached to the outside air door diaphragm closing this flap. Vacuum from another line tee'd to the vacuum line attached to port 2 acts on the vacuum canister attached to and opens the recirculating air door on the passenger side kick panel. At the same time the correct water valve is closed from a lack of vacuum in port 3 line.
Port 1 is common with port 3 when the uppermost lever is moved to OUTSIDE air and then remains common as the lever is moved all the way to the right DE-ICE label.
In this position port 3 line vacuum draws the water valve open allowing circulation of coolant. Lack of vacuum in port 2 allows the spring to close the inside kick panel vent and the spring to open the outside air door diaphragm.
My 3 port control head switch could not be taken apart. it appears to be held together with a rivet through the center of the assembly. The spring clip under the large head of the rivet is keeping tension on the two halves sealing the vacuum control head switch as good as possible with 1972 technology.
Hope this helps someone.