Agreed a new thread would be great to keep this one from being mucked up with conversation about diagnosing one issue rather than the original idea to simply share how this system works and the components thereof.

 

So 2A in top diagram, Aux, goes to rear of van to rear Heat and AC module?
That run was chewed off about 6" towards Right side and is not fun to reach, wondering where it pops out again so I can splice into it...
A 1996, but seems to follow most of what you use other than the actual controls..

 

To anyone tempted to add a comment or seek additional help or input from me PLEASE DO NOT post it here--do that in the open sub-forum for the E-Series--I will not respond or reply here any longer!

 

I know the last post was over a year ago but this is where Google took me and at the very end of the thread was a person asking the exact same thing I was trying to discover and had not been answered in any other link provided by the search engines. If someone else ends up here in the future, I want them to benefit from what I figured out. A big thanks to JWA for this thread and detailed videos.

I too had the issue with my A/C output changing from the dash vents to only the defroster outlets during high engine RPM (low engine vacuum), such as when climbing long mountain grades. I had a vacuum leak but it wasn't due to the vacuum reservoir tank like many Ford vans suffer from. I knew I had a leak somewhere between the vacuum pots in the upper dash and the 2A vacuum motor. It is a long path from front to rear and with a few twists and turns but I found the path and my leak.

The blue micro tubing that leads to vacuum motor 2A, leaves the dash pots area under the top dashboard access lid and goes acoss the dash (still in the interior) and then down the frame near the driver's left foot area and emergency brake pedal. It then goes under the driver's side step well insert and is hidden inside the electrical harness, completely under the removable plastic step well insert. That is where I discovered the break in my line and it was easily spliced and fixed with some thick wall silicone tubing. From that point, the blue line follows the harness under the step and rearwards to just behind the driver's seat where it turns and goes up towards the roof. There is a factory splice in the tubing just after it transitions to vertical. From that junction, the line goes up into the roof and then back and down to the rear A/C/ heater assembly.

Photos 2&3 show the driver's footwell area with the step cover removed. This van has a lot of rust from being used as an employee transport van at a copper mine in New Mexico so lots of cautic materials used around the mine really ate up the body.

My temporary fix to keep cool A/C air blowing on my face during summer driving.

This is a rusty van. Spray foam was used to fill in the jagged holes around the harness

There was about a 3" section where the tubing was quite brittle and powdery on the surface. I cut that section out and slipped on some heavy-walled silicone tubing over the ends.