Weird central door lock problem - '91 300CE

[rgnprof]

I bought the car w/o a pump - long story but the previous owner had someone try and fix it and they replaced the pump, but it didn't work and he took it and never got back with her...

Anyway, I bought an eBay pump - part # 124 800 11 48, which I think is the original number. It worked once and then quit, leading me to think I shorted it out when I installed it. Bought a new Hella pump - 124 800 21 48, and it won't even run. I took the ebay pump apart and fixed what looked like a bad trace on the circuit board and hooked it directly to 12v - runs fine in both vacuum and pressure modes. Installed it and it still doesn't operate the locks - makes kind of a grinding noise for 20-30 seconds and then gets quiet - if you lock any door, the grinding/whirring noise stops.

I have checked all of the wiring/pneumatic stuff via the FSM - no vacuum leaks and I have voltage every where I'm supposed to except at the trunk. I pulled that actuator and tested it following the procedure outlined in the FSM and the actuator tests fine. But, I have no voltage at the trunk connector. I have not pulled the door panels yet...

Also, the closing of the windows and the sunroof using the key - when turned to lock - works sporadically. Actually, one time it rolled up the passenger window only, then it didn't roll up any, then it rolled up the driver's door and the sunroof - now it doesn't do anything. Is this connected to the door locks, maybe?

And, do I have the right pump? The new Hella pump is not exactly like the other one, nor is it exactly like the one on Worldpac. It has an extra single pin connector and no plastic connector where the flat plug connects...

ryan

[mbdoc]

ON that c-48 w/o ortho seats, the 124-800-21 is correct.

With the electrical 2 pin connector connected, do you have 12V to the plug?

[rgnprof]

I have followed the FSM and tested voltage several times. There are 2 plugs on my pump - a round one with 3 prongs and a rectangular shaped one - also with 3 plugs, although one is a dummy plug. I have 12v at the red wire/ground wire (the 2 outside wires) on the rectangular plug - and I have 12v from the ground to the middle wire with the key on.

I have also tested the voltage to the 3 doors (driver, passenger, trunk) by connecting my multimeter from the ground wire on the rect plug to each of the 3 wires on the round plug. I have checked this voltage with the doors locked and unlocked (6 tests) and I have 12v each time EXCEPT at the trunk with the doors unlocked!

I pulled the trunk actuator and have tested it - again following the FSM procedure. All of the ohms measurements check out per the FSM specs, but I don't have any voltage at the connector. The FSM says to check:

1) "test contacts of connectors
2) Test continuity of cable terminal 30 (rt/sw or rt/ws),
3) ground cable (br/sw or br/ws) warning buzzer contact S8/2 and its
ground"

I'm not exactly sure how to do these tests...

The ebay pump runs (sounds funny to me), but I can not get the new Hella pump to make a sound - is it possible that I got a bad pump from manufacturer?

Also, I am attaching a wiring diagram - it looks like the door lock pump IS connected to the convenience control system - am I reading this right? Could these problems be related? Wiring diagram is top left in the album...

http://s511.photobucket.com/albums/s360/rgnprof/Mercedes%20300CE/

Thanks for any help!
Ryan

[rgnprof]

I'm still stuck! Received my second vacuum supply pump today (Hella) and no go. Again, I can not hear the pump running at all. I am attaching link to the electrical testing procedure - could someone read thru this and tell help me make sure I'm doing this right? It is 80-104.

http://mb.auto.pl/index.php/Dok.-serwisowa-CD2.html

I'm not sure why you have to take the plug apart - on my pump the middle prong of the straight 3 prong connector is a dummy prong...

The second set of voltage tests all check out EXCEPT one - I have no voltage to the trunk actuator when the trunk is unlocked. Would a bad trunk actuator cause the whole system to shut down?

ryan