Many times on the W108/109 cars the wiring harness that plugs to the sending unit in the trunk is too short. Most of the time you will find broken wires at that connector.
THE only contact points are for the reserve light.
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
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190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)