JimGibson

Hi all... I have a 1997 Mercedes C280. The A/C blower motor resistor went out and I bought one from an online parts store to replace it. When I replaced it, the fan wanted to run at a low speed at all times, even with the key off. I sent the resistor back and they sent another one... same problem.

I have been pulling the fuse under the hood every time I stop the car to keep the fan from running just so I can have A/C when driving around here in the hot Florida sun.

I tested the wires coming to the resistor and the white wire in the middle is always pushing a couple of volts even with the key off. That is why the fan is running even with the key off. Is this wire supposed to have constant low voltage? If I increase the fan speed with the dash control, the voltage to this wire increases, so I figured it is the one with the problem. There are three wires, one always hot at 12 volts (even with the key off), one ground and this white one in the middle.

Is the constant low voltage coming through the white wire the problem or is it that the resistors are bad and they aren't shutting down the low voltage like they should? They cost around $40 each, so maybe they are just cheap parts. Do I need to buy another, more expensive resistor?

I appreciate any help you can give me. I sure am tired of messing with this fuse every time I start or stop the car...