What is this in/behind-dash located light bulb for?

[donbryce]

I was removing the instrument cluster in the 560SL, for the umpteenth time, and found this. It was kind of shoved under the left air nozzle area, next to the light switch, behind the dash. It has a rectangular socket that doesn't fit any hole in the cluster. Anyone know what it's for? I tried all the lights and ignition positions and it didn't light up.....

[meltedpanda]

may be the light for the center indicator for the head lamp switch ( when you pull it out for fogs for instance
other possibilities
rear window defroster
radio? ( do you now have an aftermarket?)

what color are the wires, you can always trace them on electrical diagram

[donbryce]

I was, fortunately, in the process of removing the wood dash trim strips, and had to remove the left side speaker, the main light switch, and the piece of plastic ductwork on the driver's side air nozzle to get at the far-left bolt on the driver side trim piece (see other thread on this). With a mirror, you can just see the square hole that this bulb holder fits into, on the back side of the light switch plate, just left of the switch hole.
It was a pain to replace this bulb, even with all that stuff out of the way. You need to work through the speaker hole with a mirror, and even then, you can't really see it fit into the hole, have to feel it. I broke a bulb putting it in.

"may be the light for the center indicator for the head lamp switch ( when you pull it out for fogs for instance" Thanks for the input. That bulb is in the tip of the switch itself. You'll see it when you pull the switch button off to access the retaining nut.

Update: The switch bulb doesn't illuminate when the knob is pulled out and turned to turn on the fogs....must be another wire needed, or some hook-up at the switch itself that was done wrong by a PO. The little icons on the switch bezel light up now though, when the lights are on, and look really cool....they don't in my 380SE, betcha it's the bulb there too.