I agree, the connect might be corroded. Mine has the fog lights enabled when you pull out on the light knob one small click. It is a little interesting I think that my W123 300TD diesel wagon fog lights only engage when pulling outward on the knob after you have turned the light switch two clicks CW to turn on the running/driving lights. The 230SL fog lights can come on by pulling outward after only one click CW needed, without the running/driving lights also engaged. This seems like the correct was for the lights to be wired. I wonder why MB wired those later diesels to only engage fog lights whenever the driving lights were also on? This seems like folly, or am I missing something?
-CD-
1967 230SL
1983 300TDT