carl141160

I have a 1999 SLK R170 and the heater fan will not work on any speed, also the heated rear window switch does not illuminate,is there a control module for the heater fan or does it only work via the rheostat. this car has been in storage for the past 3 years and everything worked beforehand.

Alex.currie44

I cannot speak to the rear window issue but suspect a fuse or a nibble wire.
As to the fan see below. You will need a meter.

The three prong connection that attaches to the regulator(resistor) should always have power from the red lead, the brown lead is ground, and the white/pink strip lead is controlled by the fan switch. With the car off, and the fan switch in the "off" position, there should be no power to the white/pink lead. With the car on, the voltage to the white/pink lead should increase as the fan switch is rotated from "off" to "high".

If there is constant power to the white/pink lead, the control panel is defective. If there is no power to the white/red lead, but the fan still runs, the regulator(resistor) is defective. That's my issue - no power from the white/red lead, but the blower motor still runs. This is a common problem - the regulator(resistor) fails "closed" and provides power to the fan without power from the controller (fan switch).

Resistor PN A 202 820 73 10