I am trouble shooting my central locking system (1987 300E) and it passes the voltage tests with the exception of the passenger door lock.

But I cannot get the vacuum pump to operate using the car's electrical system as designed. I can however get the central locking system to operate if I run 12 volts directly from the car's battery to the pump motor and then use a second hot line to serve as a control to activate the power at the pump motor.(lock the system) I can then reactivate the motor (unlock the system) by using a ground wire as a control.

Both my connectors : three pin and two pin have 12 volts at the pump assembly.... but the system will not operate from that voltage.... it operates only from direct battery voltage.

I checked the amperage of the two pin connector (power to pump motor) and it has only .04 amps at 12 or better volts. It seems to me that there may not be sufficient amperage in the cars central locking system to operate the system.

Does anyone know what the problem might be?

Also I cannot find the connection X48F. My documentation says that it is supposed to be at the Right Rear Door Sill Area. Does anyone know what this junction/connector looks like and where it is located on an 87 300E?

Smiles.



[Edited by ejsharp on 05-07-2001 at 04:20 PM]

__________________
Earl



1993 190E 2.3
2000 Toyota 4x4 Tundra

earl,

Did you check the powered wires only, or did you check the ground wire as well (without ground, the pump won't function either).
I think that the X48f connection is one of the two connectors at the pump (these are the only connectors near the right rear door sill as far as I can remember).

greetingz,

__________________
1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)

To test the ground, I used direct battery voltage and the ground wire at the pump motor. The system will work under those conditions.

Seems not to have sufficient amperage in the hot lines. I do want to check the grounds but I cannot find them. Anyone know where the ground points for the system are located?

Any other ideas where or what junction X48F might be?

__________________
Earl



1993 190E 2.3
2000 Toyota 4x4 Tundra

You need to verify the voltage in the wire RD/WT (red and white) while connected, while operating the system. You undoubtably have resistance in either the power or ground leg. The difference between the voltage in that wire and battery should be only a couple tenths of a volt. You will need to back probe or pierce the wire as you have to test it under loaded conditions. If it does what you think (provide battery voltage and ground) then it will work just like any other source of 12v and grnd.

The blue wire, green wire, and yellow wires represent the control signals. make any of them hot (battery voltage) and the door should unlock. make any of them ground and the doors should lock. The Red/White is unit power and the Brown is the unit ground.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Thanks for the explanation Steve.. I have come to the same conclusion. My problem is that I cannot trace the wires. They disappear under the floor of the front seats. There is a junction somewhere named X48F. It's a distribution center or hub for the red/white wires which carry constant battery voltage for the components of the central locking system.

I have taken the car apart looking for it. Panels off the doors, pillars... removed back seat, taken up the mats and sub flooring and I cannot find X48F.

I feel rather certain that the power loss is related to that junction.

I have located the junction for optional equipment under the driver's side kick panel. The power breaks down in the wires between that box and the passenger door (no voltage in red white). I have current in the driver's door and the trunk... also at the pump. The passenger door fails the unlock test when testing control voltage.

Will check it further tomorrow. Can you look up the location for X48F and verify its location in an 87 300E?

Smiles

__________________
Earl



1993 190E 2.3
2000 Toyota 4x4 Tundra

The x48 connector is described as being in the RH rear door sill. We had a similar problem on a 300E and the problem was some where under the carpet (I saw the damage but don't remember except it was on the floor - could have been under a seat. The connector you are looking for x48f is grouped with x48d and x48e. The other connectors x48a,b,c are identified as antitheft harness, described as base of right hand door pillar. Unfortunately there are no pictures for that connector.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Ok Steve... Thanks. Thats a big help. I suspect that the connector(s) that I am looking for are actually the female connectors that run off the distribution male pins of circuit 30 (for optional equipment). It is located under the kick panel (drivers side next to foot parking brake pedal).

I suspect a break in the wire to the passenger door somewhere under the seat. I also suspect the female side of the red and white at the pump. Will check it out this evening.

Smiles.

__________________
Earl



1993 190E 2.3
2000 Toyota 4x4 Tundra

I spent a few hours this evening further checking out the central locking system. I cut open harnesses and traced wires. The circuit runs from the distribution box of circuit 30 located under the kick panel of the driver and goes under the driver's seat and passes through the plastic conduit that runs along the floor and under the seat. It then distributes r/w wires to the passenger door lock, the trunk lock, the pump, and then returns back out from under the front drivers seat and goes to the drivers door lock.

When I began working on the whole circuit was hot except for the passenger door lock. But while moving things around ... sliding the seats back and forth in order to gain access to the harness... the whole circuit went dead. The wire remained hot from the kick panel to where it disappeared under the drivers seat... the return wire back to the driver's door and everything in between was dead.

So I figure moving the seats back and forth has something to do with knocking the R/W circuit out.

The problem I have is that I do not know how to access the harness that runs under the two front seats. I looked at the front seats and it appears that if I unbolt the front of the seats they might raise up and back on rear hinges. Do the front seats lift and hinge to gain access to what is under them?

It appears as though there is a break or damaged wires in the harness that runs under the seats... or there is a connector under there somewhere. The wire has to split somehow because one wire comes out from under the seat at the FRONT of the passenger's seat and goes to the passenger door lock and two come out from the REAR of the passenger's seat... one going to the trunk lock and the second to the pump under the back seat.

So I need to get to the harness under the front seats. Does anyone know how to do this?

Many thanks in advance.

Smiles

__________________
Earl



1993 190E 2.3
2000 Toyota 4x4 Tundra

In stead of getting the hardness under the front seat, I suggest a rewire from point A to point B bypassing the problem area. Do it with a wiring diagram so that you know you are wiring correctly.

David