Hello all - neighbor just picked up a '83 300D When driver door is unlocked from the outside, should all locks pop up unlocked? Also when in the car and I push down the driver door lock, all locks should go down(lock) yes? I put a mity vac on the main line going into car that controls all the door locks and could not pull a vacuum . . .. my first go round with door lock issues -

Yes and Yes. It is probably a simple fix. You just need to find the leak.

Start by pulling vacuum on the storage reservoir and go from there. A common leak is at the "egg crate" where the line goes into the side (on the bottom of the rear deck in the trunk).

Color Diagram of lock system:

W123 Vacuum InterLock Diagram

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AJ

1985 300D (SOLD)

Great diagram, thanks!