1996 Oldsmobile Aurora front Passenger window

Front passenger window will not go down. I have removed the panel and tested the motor by reversing +/- wires. The window goes down. Reassembled in the correct wire position the window motor operates correctly to put the window back up. The motor operates to place the window up from both the master switch or the switch on the passenger door. The window will not go down from either the master or the door switch when configured correctly. I've replaced the switches and motor from a donor vehicle to test for same results. That's what I got. The same results with the replaced Parts as described above. Ground is good as window goes up after putting it down by reversing wires. Same for positive. In normal config acts as if no power is there when switch is placed in down position from either side. I know how to trouble shoot most electrical problems. After three attempts of tear down and reassembly, separated by days to get my positive attitude back, I gave up. Help!