On the W140 chassis (& later cars) the fan is made on to the in-car temp sensor.
It is mounted in the dome lamp assembly.
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
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44 years foreign automotive repair
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190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)