Testing blower regulator w124
 

I have removed the fan and regulator and determined by my lack of voltage on the three pins behind the brake booster that I need an ignition switch. I'd like to put the fan and regulator back together with the wiper but do not know how to bench test the fan regulator. I tried putting twelve volts to the red wire and ground to the black wire and the fan does not work. Is this a way of testing the regulator? I also tried 12 volts to the yellow wire and ground black and the fan didn't work. The fan does work if I apply voltage to it directly. Any help would be greatly appreciated!

You need the red power and black ground hooked up then the yellow is the signal wire, which should only be 6 or 8 volts (I don't recall exactly at the moment) for max blower speed. I'm not sure 12V on the yellow was a good idea but the regulators are relatively robust so you're probably OK.

Wow, a pm and a response already!!! Thanks for the info. My regulator is ok and I can at least put the fan, regulator and wiper back together so I can remove the tarp from the front of the car. Now onto the ignition switch.....