I was driving my 1997 E420 sport yesterday when stereo quit and also found when I parked that the door locks did not lock/interior lights were out (and no multi-contour seat on next start-up.) Checked manual for fuse location and found no fuse assignments in manual, or on cover of fuse block, or anywhere for that matter (BTW, would it kill MB to give us this info?) Had to call IT for fuse location (under back seat) and number (5).

Replaced 25 amp fuse and stereo/interior lights OK but no locks/multi-contour. I understand the PSE (?) pump generates vacuum for the door locks, but does it also generate pressure for the multi-contour seats?

If the pump blew the fuse once, shouldn't it keep blowing it? Is there a seperate module that tells the pump to run - and if so, where is that one? Does the pump (or control module) need to be reset like the one in my 1995 S320? I checked a bunch of posts but could not find anything on this (for the W210.)

I did put a multi-meter on what appeared to be the power supply (largest wires) to the pump and it had good voltage between the black wire and two (2) other wires (red w/green stripe I think.)

Just in case, any cost estimates on a new pump? Is there a core charge or can I tear into mine to check for anything obvious?

Does the circuit need to be reset in order to TRY to work again? If so, how do I reset it?

I located a used pump for $ 225 (about 1/2 of new) so I figured before spending the money, I would take it apart and see if there is was an easy fix.

Pump disassembly is as follows:

1. Remove bottom of pump (mine was blue) by releasing all the tabs around the perimeter with a small screwdriver.

2. You are now looking at the bottom of a printed circuit board. The ends of the board have the plug sockets on them and are loose, but the center of the board is held to the valve by three (3) small hex head bolts. Remove these carefully as they are very close to several surface mounted components and lands.

Note: Static electricity can damage parts of the board so try to only touch the edges.

3. The board does not come up very easily as there are o-rings on the connections between the board and the valve. I pried up lightly on the board in the area where the hex head bolts were and alternated from side to side with a screwdriver. It will pull straight up off of the valve.

Note: My board had a burned out land on the bottom. It was located about an inch from where the motor leads come off the board and was very easy to spot.

4. The wires that connect the board to the motor and the valve are long enough that the board can be swung out of the way. the motor lifts out and has one (1) hose connection and two (2) wires, black and white. I cut the wires to the motor about 2 inches from the board so it could be tested by itself.

5. The actual pump is the dark brown plastic part at the far end of the motor. It is held together by three brass screws. I took the pump apart because I didn't know what caused the high amp demand that burned out the land on the board, and I thought maybe the pump was bad. If you take it apart, be sure to do it over a clean bench as there are four (4) small vanes in the pump. The vanes are not symmetrical and need to be put back in the same way they came out.

6. I gave both the motor and the pump a good WD40 bath, hoping to free up whatever was causing the excesss load. I then hooked it up to a battery and ran it. The pump is actually bi-directional, allowing it to move the locks up and down with only one line. I reversed the polarity several times and put more WD40 both on the motor bearings and into the pump outlet/inlet.

7. With the pump seeming to work fine, I reconnected it to the wires with crimp connectors and reinstalled it in the assembly. The board was then put back in place and bolted down.

Note: I waited until the board was in place to fix the burned land as it needed to be stable.

8. The lands are too small to repair so I soldered a small jumper wire between two (2) of the actual component solder joints on that particular land. The bottom cover then snaps back into place.

Back in the car, the unit now works fine. It provides vacuum or pressure for the locks and pressure for the multi-contour seats just like it should. As to how long it works for, who knows, but at least I know how it works and maybe this information can help someone else repair theirs. GOOD LUCK!

Just bought 1997 e420 w210 with 132k on it for a great price(I Think)
of 2500 with it being pretty straight and clean.
it had some issues such as no blower for heat and the power locks not working.
blower was simply the resistor found one on ebay for $55 delivered, got it in 3 days and that took care of that.
the lock problem was the vac pump not working.
found moisture under the pump in the foam padding.
took pump apart and the underside of the board had corrosion in several places.
the top side of the board looked ok.
took a steel brush to the underside and removed any corrosion I could see.
reassembled and reinstalled in car, tested and sucess
locks now work like they should, and trunk release also now works.
so thanks for your description of what you did as it put me on the scent.
gemsbeme

I had a problem but it was my drivers door frame button

__________________
1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt