If the window works one way, the wires are okay. Without going into a pile of electrical theory, if you remove the plug from the motor, you should measure continuity to ground from each of the wires. If you do, that indicates two of the four sets of contacts in the switch are okay. If either wire measures open circuit, one of the sets of contacts is burned or arced.
Next, turn the ignition switch on, then when you press the switch to "down", you should find twelve volts on one of the wires. When you move the switch to "up", you should find twelve volts on the other wire. This is the test you described already, and it shows the switch is suspect.
Basically, both motor wires are grounded through two halves of the switch. When you activate the switch, one of those wires gets that ground removed, then it gets connected to twelve volts.
There is actually four switches inside the switch assembly. One relaxed switch and one activated switch are used for "down", and a different relaxed switch and a different activated switch are used for "up".
To say that a different way, suspect the switch is defective.
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Thursday, May 10th, 2018 AT 7:29 PM
