Are there any motor sounds? If so look under the front of the seat and operate the controls. If the cable guides move then it's the mechanism. If not then it could be the relay which supplies power to the seat controls. It's on when the car is on. Check the fuses and also check the relay. I think it's under the seat. You can remove it and open it. It may need to be resoldered. You could also bridge the connections at the socket so the seat would always work.

It's unlikeley all the controls are bad at once. My passenger seat would not operate in one direction so I took the controls off and drilled a small hole in the affected switch. I then squirted Radion Shack tuner cleaner in the hole which cleaned the dirty contacts. It is still working after a year.
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Warren Bain - '86 744Ti M46 >290Kmi, '99 V70Glt > 45K mi, '96 965 >100Kmi Wifemobile near Manassas Va.. Check the 700/900 FAQ via the 'features' pull down menu.