I have2 questions for owners of European spec W126 cars.

#1 Can you tell me what the color coding is for the rear fog light wire?
On the cars with the steering wheel on the left side the inner most bulb is the fog light. There is no disassembly involved other than if you were changing out a defective tail light bulb. If you remove the light cover from the trunk you can see the wires that lead to each socket. The far right bulb as you are sitting in the seat is what I am referring to.

#2 Do you have the part number for the bulb and for the socket that is plugged into your headlight switch knob? This socket and bulb is used for the indicator light that indicates when the rear fog light is turned on. It glows an amber or orange glow in the center of the knob.
If you do not know, if I could borrow the VIN for your car I can look it up myself, or at least try to look it up. If I use your VIN then I will need to know if your car was delivered in Europe versus Japan, etc.

My socket is made from plastic and is aged to the point of flaking apart when touched so I need to order a new one and my car is a 1991 N.A. US Spec 420SEL so that socket & bulb part numbers do not come up when I look at my car.
Thank You,
jimm1009 here on the forum or e-mail me; jimm1009@yahoo.com