I took the instrument cluster out to install chrome rings and when I went to put it back in the car I found this one extra bulb that doesn't fit anywhere on the back of the cluster. It's much bigger than all the others. Anybody know what it's for?

As it happens, I took my instrument panel out yesterday too.

I took pictures of the connections before I undid them in case I couldn't figure it out.

I'd say it does fit somewhere back there. It may not be clear to you exactly where, but I'm almost 100% sure there's a spot. It's different than mine, so I can't help, but here's a couple of suggestions.

Do you have a trusted Mercedes mechanic you can ask?

How about the parts counter of your local Benz dealer? They have drawings on computer to identify the bulbs.

Do you have a local Benz parts yard? Those guys usually have some answers, although not always correct?

When does the light come on? During start up? Here's your chance to be a detective.

Good luck.

__________________
MB 1986 190D in my past
MB 1987 300E on the street
MB 1994 'Smoke Silver' E420 in my driveway
1999 Mazda Miata in the fun stable
1964 E-Type Jaguar Coupe- Sold
1970 E-Type Jaguar Coupe- Sold
1968 Corvair Monza Conv. with Turbo Transplant- Sold
1986 Merkur Xr4ti- abandoned
various mundane American autos

If I'd known then what I know now...

Hell, I'd probably still have done it anyways.

I noticed the bulb has wiring leading to it. Don't all the bulbs just twist in and get power directly off the board of the cluster? Does your car have an aftermarket alarm or radar detector?

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1989 300CE

Hmmmm. The loose bulbs from the cluster in my W124 are all labelled with numbers that correspond with inlet positions marked on the rear.
(of course you need to pull the cluster out to be able to see the numbers)

All the numbered bulbs were put back in the correct holes. This has no number and is bigger than the other ones.

Could it be a footwell light?

Does it come on with the park lights? Does it come on when you turn the key to run before starting the engine?

Sixto
87 300D

Doesn't come on with lights or when you turn the ignition on but I didn't check if the bulb is OK either.