I found the connection and fixed the problem. The sill area is under the feet of the rear right passenger, You need to move the front passenger seat (not the driver) as much as it goes. Then take of the sill metallec strip under the door (in the car not the door). You should be able to fold the carpet and follow the plastic cover of the wires. You need to pull the carpet as much as you can to allow for openning of the plastic cover. I had to take of the plastic base of the car pillar at that place to get more space (it has two screws and easy to take off). Once you open this plastic box, follow the wires from the pump and tear off the covering tape. You will find that connector, it is pastic transparent. In my case it was rusted to dust. I believe the welded surface suffered from condinsation and rusted badly. I advise all owners of 124 cars (older ones) to fix this conncetor (X48F) first if they have any problem with center lock system. The problem was that there is a misleading voltage indicating that everything is Ok but not enough power to run the system.
SEARCH the forums for "X48F" there are several threads, with pictures on where and how to fix. I added my comments here for further explanation
Thanks for the nice members of these forums