PeachParts Mercedes-Benz Forum - View Single Post - Door Locks

Jeremy5848 · #2 02-24-2007, 01:10 PM

It depends on the model year...

Your car and my '85 should be similar. My wife's '87 is somewhat different.

Basically, operating the locks "manually" or by "vacuum" is the same thing. When you operate the lock on the driver's door, whether by using the key from the outside or with the knob from inside, you are activating a vacuum switch. This causes vacuum from the reservoir in the trunk (of a sedan or coupe, don't know where it is in a wagon) to go to all of the door locks, the trunk lock, and the gas flap lock, and lock or unlock all of them.

(I'm describing it backwards, of course: vacuum doesn't "go" anywhere. Air from the various locks is pulled through the tubing and valves to the vacuum reservoir, thus making the locks work. You knew that.

)

If you operate the passenger door lock with the key from the outside, only the passenger door unlocks. Ditto for the trunk. For later cars, like my wife's '87, these locks also unlock everything else. This may also be true for earlier 300SD models (126) -- I don't know.

I'm not sure about correct operation of the rear seat locks. Sometimes mine won't unlock manually from the rear seats. I suspect that I may have a vacuum leak in the driver's door vacuum switch. Like you, I need more information -- how did they work when they were brand new?

Jeremy