Testing window regulator
 

I have been working on my 86 300E. I am trying to test the motor to determine if it is shot. The wiring diagram shows two hot wires to the motor. Power feed to individual wire determines motor rotation. It seems that the switch turns one of the wires to a ground depending on required rotation of motor. If my assumption is correct then I have a broken ground wire. Can I directly connect one wire to hot and the other to ground on the battery to test the motor?
JohnO

if it is a rear window, you need to use the green & black wire at the switch.

yes you can test the motor that way, switch it to test the opposite direction, your right the control switch's switches the polarity according to direction desired

What exactly is your problem?
 

I have the same vehicle, may be I can help you!:cool: