How does one troubleshoot the 83 240D Vacuum door lock system. Service CD has no info to the best of my knowledge.
My symptom is I dont think the system works the way its supposed to; however, I'm not even sure how it works. I discovered it when I was working on the Power Window regulator, the fact that theres a vacuum circuit on the door lock.

(1) Is the driver door lock supposed to unlock all four doors? This doesnt work in my car.
(2) Driver door lock cant be locked without using key. I dont think this is normal--problem might be in the driver side door?

What is the most likely thing wrong? Do you know where I can get diagrams? I have a vacuum squeezer.