Tom,
I was able to get better access to the switchover valves by popping out the horizontal row of rocker switches above the ACC panel and removing that panel as well. Though I was not quite ready to remove the potentially offending switchover valve today, and not yet having the proper vacuum testing instrument, I was limited in my troubleshooting to pulling the vacuum output hose off the switch and seeing if I could feel any vacuum effect with my thumb over the vacuum-out spigot of the switch whilst running the ACC through its paces. I felt no such effect whatsoever, so my inclination is to think that the switchover valve either is not working or is not getting the proper signal to activate. What is this Mity-vac that I have seen mentioned? Is it something that a DIYer can pickup at an autoparts/tool store, do you know? I think I would like to apply vacuum to the leg flap actuator to see if that mechanism is working properly before I delve into the switchover valve itself. I have to assume that the vacuum circuit before it gets to the switchover valves is working fine because the other vents seem to work properly.

Dan