Bound to happen sooner or later; the snap fitting broke when I was disassembling the vacuum diverter attached to the heater/AC switch, fortunately there was enough space to install a small nut, washer and bolt.
Here I have the diverter and connecting plug back on the back of the heater switch. While still apart I tested each dirverter line with a brake bleeder vacuum pump and using the service manual to tell me which vacuum operated door should be open.
I was able to visually check every door except the AC door which is buried behind the gauge cluster and the water shut-off valve as it was toast. Here is the outside air valve located on the right side below the windshield and under the fender lip. The screen has been removed. I’ll add rust check to the assembly before re-installing the screen.
The rear window defroster fan and heat/AC controls back in the console. I will replace the console and then get the engine started so I can do a final test on the controls except for the water shut-off valve which is on order.