I have an 83 300SD, and the locking system stopped working very suddenly. I checked the pump with an external 12v battery and it was working, so i then plugged it back in. When i plugged the pump back in it proceeded to run by itself for a couple minutes. I then took the actuator out of the drivers door and disconnected it. next i locked all doors except drivers and put the yellow and red wires together, all the doors opened. I then locked all the doors againa and put blue and red together, again, they all opened! what am i missing here? is there a special switch INSIDE the actuator or is there another valve somewhere? this is puzzling me, i appreciate your help Ryan

The pump has a processor inside that sees the signals. Ground and power alternate to show lock and unlock. If one pod is leaking, none will work properly because the pump will run-on and time out.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

so you think my pump is fubar? any chance of me fixing it myself? thanks
R

Sounds like the pump is working as it should, and one of the door actuators has a leak. The pump keeps running, the leak won't seal and the pump times out and shuts down. You need to check the condition of the door actuators and all the vacuum line connectors.

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

If you listen very closely inside the car after locking (and/or unlocking) the doors, you might hear which door the leak is coming from. This might save the time of taking off each door panel and inspecting each individual actuator.
Good luck.

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)