Remove the control box (driver side kick panel)(do a search on this here), remove the printed circuit board, arm yourself with a good light and magnifying glass, then using a fine low watt iron, re-melt all of the connections on the board except the IC ones (black boxes, they don't like heat). From others posts and my own experience, this will fix it 90% of the time.

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1986 560SL
2002 Toyota Camry
1993 Lexus