It has occurred to me that there might be times when a driver might need to unlock the driver's door without unlocking all of the others. Such situations might involve a "bad neighborhood" or a woman driver alone -- you get the idea. Here's what I am planning for my '87 300D Turbo (W124, OM603). This should apply to all 124s and to other MBs with an electric Central locking System (CLS), such as the 126 and the 201. Sorry, this method will not work on a 123. You would have to do some vacuum line plumbing.

You probably know that the mechanical key-cylinder locks in the driver, front passenger, and trunk/tailgate doors have an electrical switch. When the key (or the inside knob) is used to lock or unlock the door, the electrical switch operates the pump and locks or unlocks all of the other doors. To defeat the CLS, all you have to do is to disconnect the wire from the driver's door to the pump.





In the 124, this wire is blue and it attached to pin 2 of a round three-pin connector that plugs into the pump, which is under the right side of the passenger seat. In the 126, the pump is in the trunk. I don't know where the pump is in the 201. With the blue wire disconnected,
(a) The key (and the inside lock knob) will continue to lock and unlock the driver's door but will not operate the pump so none of the other locks will lock/unlock;
(b) The right front door and the trunk/tailgate will continue to lock/unlock all of the other doors through the central locking system as usual;
(c) If you have an aftermarket keyless remote system, as I do, it will continue to operate normally, locking and unlocking all of the doors.

If you need to restore normal functioning of the CLS on a regular basis, you could install a switch with "Normal" and "Defeat" positions. In "Normal," the blue wire from the driver's door to the pump is connected; in "Defeat," the wire is disconnected. This switch could be put in the dash, hidden under the seat, whatever you want. Having this switch is more important if you don't have a wireless remote system.

You can also get more sophisticated. For example, instead of breaking the blue wire from the driver's door to the pump, simply break the +12V wire (red w/white stripe) at the switch in the driver's door. (This requires removing the door panel or the left front kick panel to access the wire.) By breaking the hot wire, the key switch and inside knob will continue to lock all of the doors but will unlock only the driver's door. The reverse could also be done by breaking the ground (brown) wire. Then you could unlock all of the doors from the driver's door but you could lock only the driver's door. Why you would want to do this I cannot imagine.

Jeremy

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Our all-Diesel family
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