I just had my 2001 SportTrac in the shop for this problem (or a similar one). Wife says LR T/S not working. I get in truck (put up tilt wheel) and it is ok. Again, wife says, LR T/S not working. (I dont move tilt this time). Replace bulb, stilll not working. I tore whole back end apart to trouble shoot, no joy. Get in truck to move it in the driveway, wove tilt wheel all the way, turn signal worked.
Dealer found pin pulled out of MFS connector, had to replace it and pull some slack up in the harness.
Hope this helps, try it and see.