Have a 1982 300SD. Previous owner had a problem with the blower motor circuit. That person soldered in an ATO fuse holder and had a 25 amp ATO fuse in it. I've blown that fuse a couple of times since I've had the car, and started to look at reasons why today.

Pulled the blower motor. Looks like it has at least half of the brush material left. Rigged up some wires to a battery. It blows strong, runs smooth, runs quiet, all in all, seems fine.

There's a "resistance group" down below the master cylinder, but it appears to be ok - I don't see any melted resistors. How does one check the resistance unit? Looks like fun to get out.

What else is in the circuit of this fuse? Does all the power go through the CC panel. or are there relays somewhere?

Down on the blower housing, there are two electronic boxes, one labelled something like temperaturecontroller (in German) and another electrical box on the other side. What are these for?

Other symptoms to blowing the fuses - every once in a while, it takes a long time for the fan to even start to spin. It would sit still, then all of a sudden take off.

Thanks for your help
Fred