Are you getting enough volts to the motors ? What voltage is the battery and what is the voltage when the engine is running ? There could also be an earth problem that will produce the same results.

 

I took the motor and arm out and tried just moving the window up and down in its track. It gets stuck. The rubber tracks are shot. Not salvageable. Anyone know the best place to get the rubber for these tracks?

 

try a junkyard, Buicks, Pontiacs, Cadillacs, the higher GM cars from the 1980's. the window motors are GM also.

 

Gregory,
THX - Perfect solution, just used some CRC Electrics Spray Cleaner on my driver's (LHD) window switch, presto working like new!
Never panic, work the problem, consult the formum, then retain the knowledge!
Cheers,
Chuck
Caretaker 1982 XJ6 S3