420 benz, not sure if your 420SEL has a 30-amp strip fuse on the driver's side shock tower. It's enclosed in a small black plastic case and has a philips head screw on either end. Typically the strip fuse develops a hairline crack which results in the blower motor not working. If you loosen the two screws it will be obvious if the strip fuse is cracked. If so, replace it.

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Fred Hoelzle