Most likely its the switch.

If the 2 wiring diagrams I have in front of me are right they are wired up pretty much the same in the 89 and the 93. So there shouldnt be any problems there. Both use all the same fuses and wire colors between both years.

Note - I comparted a 89 GT to a 93 GT. Not sure if its the same for verts and 4 cyl but it probably is. Free information so cant sit here all day looking up every combination. Good luck.