The problem with the Haynes manual for the W123 series is that it was printed in England. You'll notice that some of the wiring diagrams are for UK models. Haynes and even Chilton manuals are general manuals. The offical MB manuals would be best of course.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member