Head scratcher. Every function of my driver side Master Power Switch is working with the exception of the front driver side window which does not respond to the down command (DOES GO UP). I removed the Driver Side window motor and read the following voltages at the window motor plug:

- 12V @ DK BLU wire with switch UP/ 0V when DOWN
- 0V @ BRN wire with switch UP/ 12V when DOWN

So the Master Power Switch seemed to be doing it's job as it was sending the correct voltages to the motor plug. I figured motor was bad, bought a new one plugged it in- same result (responded to UP but not DOWN). So I connected original driver side motor to the passenger side just for kicks- it worked fine there! This meant the motor was good as it responded to both up AND down commands from Master Power Switch.

WHAT GIVES,
- Master Power Switch seems to be good as it's sending correct voltages to window motor plug
- Driver Side motor also seems to be ​good as it responded to both up AND down commands (although only when connected to Passenger side and not driver side)

Maybe I'm overlooking something as this would seem to defy logic. Any help would be greatly appreciated . Thanks a bunch.

 

I would take the switch apart and clean the contacts or try a different switch.

 

Thanks oldchevy, ill try that.

Wouldn't the switch be working properly if the voltages are showing up at the motor plug every time you press up or down? I did notice when I removed the Master Power Switch assembly that it was lightly coated all around with a white powdery substance- kind of like the residue left behind after sulfur burns...the passenger side assembly did not look like that.

 

The voltage may be present when the motor is disconnected and the switch is activated. This is called open circuit voltage. Can you measure the voltage with the motor connected?. You will most likely not see the voltage with the under load condition. My 2003 has a Driver Door Module that I am assuming has electronic components. A failure of a component may cause the open circuit voltage to be present but not provide enough current capacity to drive the motor. In which case the voltage goes to zero upon activation of the switch. If your 2000 has a driver door module. I would be suspect of that module. This is all just theory. I have not experienced such a failure.