My 1991 W126's climate control lighting operates normally after being turned on, but after 10-15 minutes goes out ... other dash lighting is OK.

I can tear assembly apart and start troubleshooting, but wondered if anyone has seen this before?

Thanks for any advice in advance!

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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg