The PO had cut the vacuum/air pump power cable and the plug is not present. The old pump had shorted out. I have a new pump but the plug is no longer available from MB. I found a plug in a wrecker but the plug itself disintegrated when removed. I do have the wires and pins, though.

I would like to make my own plug out of a rubber stopper however I need the wiring diagram. It is the apparently standard 3 pin design for locking and unlocking only (no seat functions). This is on a '83 300SD. The wiring diagram states what the pins do but does not show which pin is which on the pump itself.

Does anyone have a diagram of the plug showing the pinout?

Try this, it's the way it is on my car. The diagram drawn on the upper left is as if you are looking at the socket on the pump

Attached Thumbnails

 

__________________
1983 300SD
200000miles

*Edit* - see below

I appreciate the drawing but I tried it this way on a new pump and nothing happened when trying it on a 12V battery (negative - brown, then positive blue for one test and positive yellow for the other).

On my unit the plug is round and there are two tabs on the socket on the pump. A large tab on the outside edge of the pump and a smaller tab on the inside edge next to the raised portion holding the electronics, motor, etc. I was assuming that the flat side shown on your drawing was against the large tab, facing the edge.

(Edge meaning the short side as the outlet is on the corner of the pump.)

*Edit* After looking at the corroded remains of the original I figured it out. Hold the pump with the plug outlet on the lower left hand side. The pin towards the "top", furtherest from either edge, is ground. The one to the bottom right, closest to the long edge, is pump. The one on the left, closest to the short edge, is vacuum.

One note if anyone else is testing their unit is that once it has done a cycle in one direction it will not run in that mode until you run it in the other mode. So if you do a vacuum until it stops it will not run a vacuum cycle again until you run a pump cycle.

Thanks, Phil!

I noticed that I reversed the blue and yellow wire in the diagram but I corrected it now. When you test the pump if the tube is NOT connected then hold your finger over the fitting the tube would connect to so it will switch between lock and unlock. The pump has an internal switch that uses pressure or vacuum to change depending on what it is supposed to do and if it can't sense pressure or vac build up it won't change.
Look at post #13 on the attached for a discription of the system.
Door locks 1982 300SD W126

__________________
1983 300SD
200000miles