Strange problem: whenever my climate control pushbuttons are set to AUTO LO or AUTO HI, the car shuts off perfectly, nice and quickly. But, when the OFF pushbutton is pressed, turning off the fan, then the car takes a few seconds to shut off -- as if there's not enough vacuum getting to the engine shutoff.

My climate control works great, and the rest of the vacuum in the car works well too -- doors lock & unlock, but sometimes they lose vacuum when I haven't been to the car for a while and won't unlock when I unlock the driver's door.

I feel like there's a leak in the pushbutton controls when I am in the OFF mode. I don't know what to check for, though, since I haven't been able to find a diagram of the pushbutton unit itself. I made a colorized version of the vacuum diagram that might help someone sometime, but I can't seem to figure out what happens to the pushbutton switch in OFF mode:



Any ideas?

Thanks!

__________________
1980 300SD (daily driver), 1981 300D (Inca Red)