I use fogs on my 81 300D as DL's. On my 126, I can turn the switch one click clockwise and pull it out to operate fogs without headlights (parking lights work, also). I removed the switch on the 123 and in vestigated possibility of modifying the wiring to work like the 126, but I was unable to do so. I determined which terminal powers which lights, etc. I was hoping I would be able to merely move or add a jumper wire or two simply on the switch. Finally, I ran a wire (to close the relay) from parking light terminal (one click clockwise) to a new relay in the relay box on top of left front wheel well; then I ran a wire from the relay back to the parking light terminal on the switch to operate the fogs. I think I got power for the relay/fogs from appropriate size fuse in fuse box. It has been about a year since I did this. I may have forgotten some of the details. Wish I had drawn a diagram, etc. Investigate the switch; I think you'll see how you can do it.