my left rear window was not working when i purchased the car, took it apart found bad motor, replace it with used one. it would go down but not up on rear window control replaced switch with one i knew would work same problem change switch in front center console same thing the right passenger window works ok i think they work together.. took regulator out and hook straight to a battery it works fine, now im lost

The switches ground the window motor, so likely you have a broken wire in the flex boot at the door opening.

Check to see if the wires ground when the switch is operated, then see if they are both hot with the swtich neutral, ignition on.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!