I am trying to help a lady out here with a non operating blower on the car mentioned. To do it right takes a good bit of $$ for parts (MB recommendation). I can take the existing fan out, put 12 volts to it and it blows great. Tried changing the regulator to the one from the W140 and it worked for a day or two.

I'm going to recommend installing a separate controller for the hvac fan.

ebay DC mtr controller

Has anyone ever tried going this route?

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Jim

You can get a correct aftermarket part on EBay cheaper than that...

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra