Rear power window only works in up position but not down on 1999 Malibu: No codes

Question:

My rear right power window is only working when in up direction but not going down. I opened up the door panel and it seems the wires to motor are shorted because both of them have power. When I removed the motor and bench tested it, the down position would work if I reverse the ground to power supplies. Is this a switch problem? How do I check it?

ATS Advisor:

The power window works thru your master switch at the drivers door and also at the right door itself. It is done by reversing the polarity of the motor windings which is the job of the master switch. On your master switch, there are 2 wires coming out to your right door switch: light green and purple wires. When in up position the light green wire is the ground and on down, it's the purple wire. This is done thru the electronics module inside the master switch. When applying in either position and both of these wires became ground at the same time, then the master switch is defective (same if these wires are both 12 volts as in your case). However if the ground supply is reversing to either wires, then the problem is the rear door switch.

ATS Tip:

To understand this fully, contact ATS so you can get a wiring diagram describing the colors of the wires and their locations.