I have a 1990 300TE 4matic wagon, my passenger seat & headrest control have been working intermittently for a while. Now the seatback is way down and won't come up. Forward and back seatbase control works. I took off the control panel and unplugged the module and cleaned it. Still doesn't work. All wires are connected. Guess I will get a voltmeter and test connections. Any other connections I should check? Any suggestions? Thanks.