My tach seems to have a mind of its own. Some times it works great and others it will show up to 6000 RPM at an idle. I would think that the sender is faulty. My question is where is the sender? How does one check it out? If it turns out to be the head are they avialble in reman? From who? Thanks for your help.

I think your car may have the diagnostic plug located on the L/F top of the fender under the hood. The plug is round and black in color usually. The plug has a control unit inside of it that processes the signal for the tach.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM