Hello All:

I have a 1985 300D with a vacuum issue. I had a run-on engine, and traced the problem to the master vacuum switch in the driver's door. I replaced the switch and now the engine shuts off immediately. Problem is, now the vacuum door locks don't work. I drove the car a few miles, turned off the car; engine shut off immediately. I though all was well, but when I attempted to lock the doors, only the driver's door locked.

Any suggestions? Given that the engine shuts off immediately, I doubt there's a significant leak in any of the doors' actuators...? Is it possible I have the three lines going to the main switch incorrectly installed? Can anyone confirm the "correct" placement?

Thanks in advance for any help!

Stephen

1985 300D
1999 Audi A4

If it was myself I would have to say it is entirely possible for me to hook the Vacuum Lines in the wrong place; unless I had drawn a picture or taken a photo of it before I removed it.
It is also possible that when you removed it that a Line got yanked and disconnected somewhere un-seen.

__________________
84 300D, 82 Volvo 244Gl Diesel

Welcome to the forum.

You've replaced the vacuum switch in the drivers door and it locks and unlocks correctly? Does it do this when the engine is running? Does it do it multiple times when the engine is turned off? What were the locks like before the swap? Do the A/C flaps seem to operate correctly? Do you have a Mity-Vac?

These are some of the data points useful for troubleshooting vacuum. They can start pointing you to the source of the leak or incorrect connection. There are a few threads with vacuum diagrams.

For the master switch in the door and the three lines for the sedan:
Yellow - center, "supply"
Yellow + red - left (or short tube) lock (mnemonic: red = stop)
Yellow + green - right (long tube) unlock (green = go)

Looking in the "Ofishial" FSM for the W123. section 80-020

There are 3 lines running to the vacuum switch on the drivers door.
Suction line to vacuum switch (27).....Yellow
Interlocking line (25).........................Yellow-red
Unlocking line (26)...........................Yellow-green

The left side the slider is on is #25
Center is #27
Right #26


Installation

Connect vacuum switch to door lock

Attach vacuum switch with oval head screws
in such a manner that switch will be hard to move
within is`s oblong holes.

Slip connections (rubber hoses) with interlocking line (25)
unlocking line (26) and suction line (27) on vacuum
switch.

Run engine for a short moment, insert door key
into lock and open and close.

Note: Central interlock should already respond before
the key is at it`s respective end position.

Adjust plastic vacuum switch in such a manner that
the outer edge of the switch in unlocked condition
(in sedans) or in locked condition (in coupes) is in
alignment with center of adjusting groove.

Looks like in the drawing, the groove in the slider has to be lined up with the edge of the switch body.

Attention!
if the adjusting range is inadequate, extend oblong
holes (slots) in holder by filing.

Charlie

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

thanks guys! I do indeed have a mighty vac, and confirmed the problem is the master switch. doorlocks were working fine one day and had been for years, and the next day I had a run-on engine.

I'll tinker around a little, but thanks so much for the hose arrangement info.