Take the ashtray part out of the ashtray itself and remove the 2 phillips head screws you see underneath. This will give you access at the back of the ashtray and simplifies removing the radio.
The radio and lighter share the same wire that goes to the fuse box; the wire to the radio comes from the wire in the lighter plug.

greetingz,

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1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)