For above thread posts from dgtlmn and others,
My CD trunk changer never worked since I owned car either (I am second owner of this euro model car I imported-600SEL). Following above inputs, I easily took out two 10mm bolts on trunk floor, holding CD assembly, looked at bottom of CD changer, noticed a fuse holder assembly in the changer body. Inserted a 10amp fuse (later read a downloaded Becker guide that it should be 7.5amp), and the CD changer now works perfectly-all functions completely ok.
Am somewhat weary the fuse had been removed for a reason (draining the battery), but I will monitor and re-inform all.
Thanks to all for this thread of info. Changed my life.

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Bill & Monika Mercer