Bear with me, I've searched (and searched, and searched, and searched), and I can't seem to find any clues . . .

I've had vacuum issues since I got the car ('81 300D), and just disconnected the door locks and the ACC years ago. I finally decided to give it another look and I'm getting closer. I believe that the vac switch on the ignition switch is losing vac when the engine is running. Figured this out by testing for adequate vac presence coming from brown line while engine running (doors locked or unlocked, ACC on or OFF). While the line to the switch is plugged, door locks and ACC function normally. When the line is connected to the switch, the ACC doesn't get enough vac to switchover to recirc. SO, I've got that part on order, should be here tomorrow.

Now, part two, the baffling issue. I seem to be losing vac when the ACC system is connected, but off (blocked off lines to ignition switch and door locks and put a vac gauge in place on vac lines on engine side of firewall). When the ACC is on, the system shows plenty of vacuum, but when it is off the vacuum in the system drops to near zero. So, if I have all lines connected there isn't enough vac to operate ACC or quickly shut-off engine. If ACC is removed, engine will shutdown. If shut-off system is removed, ACC will function. I've got enough vac to operate only one leaky system at a time!

SO, the question is, where can I look for vac leaks in the ACC system when it is off? I pulled the lines to all of the pods and it doesn't seem like they get any vac unless the system is activated. My ACC control unit has been disassembled and re-soldered. There appears to be a master switch-over contraption behind the dash, above the ACC control. Is this where I need to be focused, and if so, how to I go about finding the leak? I've examined the vac diagrams, and they are helpful, but I need something that explains where vac travels in different states (system activated or not).

Thanks!
Eric

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1981 300D - {172,000}
1971 220D {Sold to TomJ}

Can't help with procedure, But I would start with switch over valves. They do leak.

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1983 123.133 California
- GreaseCar Veg System