PLEASE HELP! 500 sl power window

Passenger side power window won't operate. It makes a quiet rattling sound but wont move the window. Motor is fine (switched it to drivers side and it
works). Also when I bring 12 V to the motor leads with booster cables it goes up and down fine. Mechanism is fine. Dash switch pulls in relay behind passenger seat. Switched switches with driver side just to be sure. Fine. Bottom limit switch working properly (checked with multimeter). Is there an upper limit switch? I have 12V at black and green terminals mounted on door but no movement. I'm thinking faulty ground but when I connect booster cable from door directly to negative battery terminal it doesn't help. Any ideas?
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Are you sure it is not the relay?
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I dont think so because there are two separate relays, one for up and one for down. each of them pulls in but neither works. I would suspect them if the window would go up but not down or visa versa. Also, they are mounted on a circuit board with about 12 other relays so it's tough to check beyond a visual inspection and checking that the polarity does actually reverse at the window when the switch is toggled. It seems OK.
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