Check the fuse, I found that the one on the 300D was shot while troubleshooting a malfuctioning headlight. In fact, if you have not done so, I suggest replaced all the fuses, they corrode and loose contact.

I'm not sure right off the top of my head what type of switch the 190 has, could be a simple thermoswitch on the thermostat housing or a "combination" "switch" via the engine coolant temp sensor (do a search, I believe you pull the temp sensor wires and the fan comes on).

Should be a relay, too.

And make sure the fan turns, the bearings can sieze on them.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!