Toyota Repair: power window, 1990 toyota camry, toyota camry

Question
I have a 1990 toyota camry le. The power windo on the drivers side will engage if you try to roll it up but is innoperative if you toggle it down ward. I thought it might be the switch, but i tried another unit and it did the same thing.  I have also tried it with 2 other spare window motors I have and they had the same results. I changed the relays in the kick pannel and this has no affect. Any ideas?  If I'm not mistaken this is a reverse pullarity set up as there are only two wires, what would keep the current from reversing?

Answer
The only thing left is the wiring, although not very common it's possible that there is a break in one of the wires that passes from the left juction block into the door. Check to see that there is voltage to the red and green wires when the switch is operated, yes the voltage reverses between the two wires so if voltage is lost there then the wires going inside to the connector need to be tested for an open circuit.