Disconnecting the vacuum source caused the center flap to close- so that is a good sign. All the various flaps are controlled by solenoid valves which are not too bad to access, at least on my '88. Up front, on each side of the trans. tunnel, are two removable side panels, where the footwell vents are placed. Behind both of those panels , and I don’t remember which one is easiest, is where the solenoid valves hide. They are clipped into place, and easy to remove. You want to find the solenoid with the black vacuum tube, then you can trouble shoot it. If you PM me with your e-mail address I will send you a PDF with a pretty good layout of how things are put together.
Once you remove a side panel you will also have to remove the metal ducting that feeds the footwell vents- a couple of screws will do it. Then you’ll have better access.
You have to remember that on the MkIII, removing vacuum from the system will close the outside air doors on each blower and thereby stop airflow even though the upper level flap may remain open…
Hi guys, even if I do not fix this I have to thank all of you for all your help. Thank you so
much !! …I will look at the manual and sure I will have more questions. …
On my '88,no vacuum on the system means that the outside air door is OPEN, but automatically the linkage closes the recirc. door below each blower, so air flow continues. If the system calls for recirculate, such as full cooling, then the recirc. door on each blower opens, and the outside air doors close. ( I put a switch on my car so that I can have the outside doors open all the time, allowing some natural airflow without running the blowers at all.)
Or, the climate control module has malfunctioned.
Shipwrights decease had me rip into the whole hvac system on my 94 and yanked the dash to get to the heater control/ac box, which I pulled completely out (a real PITA job I wish on no one).
On the bright side I found that whatever system you may have, at the end of the day, they are all pretty much the same after comparing it to the box from my 86.
I also found that after 20 plus years the boxes are likely in need of refurbishment for optimum performance, but I have gotten off track and well into the weeds, which I’m sure most aren’t interested in.
Not impossible, but I found it well beyond my capabilities to diagnose and work under the dashboard to fix and test the number of problems that were eventually found. In the end, the best course of action for me was to yank the dash and pull the box.
Below is a link to another reference for the MkIII Delanair unit. It’s in Service bulletin JD 07/86, starting at page 16 of the file.
And another couple of troubleshooting guides from defunct websites, courtesy of the Wayback Machine. Some pictures are missing, but the info is good. Some of the links inside the second reference work, providing more info.
https://web.archive.org/web/20081028093646/www.far-out.demon.co.uk/cardiy/Delanair.htm
I stand corrected; you are correct that lack of vacuum opens the water valve for the heater core and opens the outside air doors on the blower housing. So has to be an actuator/ door/ control unit fault. So if door closes to upper level vent when off, unplug the actuator in that position.