Fan Blower Fuse W116 1980 300SD

After replacing the heater fan with a new Bosch unit, I seem to be having the 16 amp fuse blow on a regular basis. The fan I replaced still ran but was noisy and didn't blow the fuse. Any suggestions?

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Body and Interior Specific Aid

Chassis Model Number

W116

When does the fuse blow?

Does the fuse blow only on certain fan speed settings or on all settings. What type of fuses are you using?

When does th fuse blow

It blows in auto hi or lo w/o A/C switched on. Since it's an auto unit, I can't say at which speed. Have studied my circuit diagrams and suspect either the fan motor or the resistor block. Comments? What should resistance of fan motor be?

My best guess

I have never seen a new motor fail out of the box, but that does not mean it could not happen. If the fuse is not blowing on max defrost then I suspect something is wrong with the speed resistor.

I have also seen the climate control switch panel burn causing high resistance.

To confirm - try this. Rig up some wiring to the blower motor directly from a 12 volt battery. Use 10 gauge wire. Run the positive lead through a 16 amp fuse and run the motor. If the fuse does not blow you know the motor is ok.