Clean the contacts in the switches first with some contact cleaner, or try pressing them over and over again till they make some contact. Mine are like this as well, after pressing on them for 20 or 30 times they work. Best of luck
Kate if back motor works then fuse OK so you need to try to gently frap (tap) motors underneath seats with a small hammer. This usually gets them going if switches OK. Once you get them going you need to exercise them regularly and it is best not to keep them in full forward or back position or full up or down position.
My daughter's 164 had a balky front and back motor but luckily up and down motor worked so we could raise seat to get at F and B motor to tap it easier.
Also there has been a motor start box installed in most of these cars by now: http://www.digest.net/alfa/FAQ/164/b409102.htm check and see if box under front of seat inside covering or inside a cut out slit in carpet under front of seat.
If you can't get motors to work you can also try swapping switch for reclining back with other switch to see if that will make other motor work.
If none of the seat postions work on either seat then fuse maybe bad as one fuse is for all positions. It is located about where you right knee rests on center console but you have to open fuse panel door under steering column and locate yellow fuse amongest some relays above backside of radio area.