Easiest thing to do first is a visual. Remove the turn signal switch harness cover from the steering column. Look for crimped/pinched wire (the black one is for the horn), and cracked or deteriorated insulation. If you don't see anything, disconnect the turn signal switch, connect an ohm meter to pin 4 (the black wire) and ground. Look for a short (0 ohms) (or listen for the beep, depending on what type of meter you has access to) while turning the wheel. That's an easier check than yanking the wheel off again.