From some help from this forum I have gathered some info on installing some driving lights/fog lights on my 1967 w108 250s. Over the next couple of weeks I plan on documenting my little task so that others will have info on this task. Tonight I began by getting to the lead that runs to the switch. which is located behind the head light housing. Not all models are the same as years progress so if yours is different-research your metal mates.
First removed the chrome trim that surrounds the headlight housing, screw is on the bottom, then remove the four screws that attach the housing to the fender.
Behind the housing is a junction that connects the housing to the harness, our wire is within this unit, two screws remove it from the housing, then you can put the housing in a safe place. be careful the junction has a circuit board that is fragile. I know because I broke it on the other side when hunting around. With the junction removed from the housing it is free for inspection.
If you flip it to the circuit board side you will see 5 connections with wires soldered to them, except for one that is missing a wire.. Thats the bugger we want.
If you flip it over and carefully remove a plastic cover you can see all 5 wires, note that the wire that connects to the lead that has no wire on the other side is the wire we want to use(on my car it is Grey/Green,) it is a lead that goes through the wiring harness up into the dash at the light switch and is factory wired for our accessory lights
We are left with a couple options,
I thought about soldering to the lead to complete the circuit, but i chose to remove the wire from the junction completely. I will then use the connection to run priming wire back out of the fender along the harness to a 12 volt 40 amp relay and further along to complete the circuit.
I have the relay on order and is on route, so for now I am left with cleaning up the terminal junction wires and head light buckets as they were in dire need of a good detail.
I will keep ya posted as I progress