Headlight Switch 1991 300CE
 

I can only get my corner lights and my headlights/taillights to come on...When I pull the switch out to turn on the fog lamps, the switch wont stay "out", it just pops right back in...also, what is the second "pull-out" position for, I don't understand the difference between the two?

The fog lights in the front will engage (first "pull-out" setting) when the switch is in the "Headlight" position. It will retract for any other setting (like "parking lights").

The second "pull-out" position turns on an additional lamp in the right rear taillight, making it brighter than the left. While not typically seen in the US, this a "Euro" fog light feature seen on other German cars as well.

I'm not exactly sure of the thought process here, but in foggy conditions, this allows the drivers behind you to distinguish your orientation on the road (as opposed to appearing as two motorcycles driving parallel to each other perhaps?).

Make that left rear in the USA--in fact it's always driver's side, so it's right in RHD countries.

Fog light switch will also stay out in park light position.

Thanks, thats interesting...

If the switch wont stay out in any position, is this an indication that my switch is bad? Is it a vacuum force that pulls the switch in or is it a spring force...What could be wrong?