No headlights on 93 GT !

Remove the plastic cover from around the steering wheel and check the wiring connectors for the multifunction/turn signal switch. You will probably find some melted plastic around some of the connector pins. These are high resistance connections that are causing your problem. Scrape the connections clean with a jeweler screwdriver and spray them down with WD40. Be sure that you clean both the male and female parts of the connection. Replace any connector shells that have melted or that have connector pins that fall out.

Try this to answer any questions you may have about the foglights.
SEE Mustang GT Fog Light Fix to fix the foglight problem. The stock wiring isn't up to the job and is overheating. The headlight switch & turn/multifunction switch are affected by Ford's wiring problem. Sometimes it overheats so badly that the plastic shells of the wiring connectors start to melt. This will show you how to add a relay to the fog lights to relieve the overload on the headlight wiring.