You might want to google up the fog lamp relay modification in case your wire harness and/or multi-function and headlamp switches are showing signs of overheating, such as flashing headlamps after prolonged use of fog lamps and discolored harness connecters associated with this circuit. There was also a TSB on this (some have considered a bandade fix), and it's doesn't use a relay which Ford probably should have used in the first place. The fog lamp circuit, btw is powered by fuse #15 (15 amp).
That aside, check fuse #9 (30 amp) and fuse #5 (15 amp) which share power supply distribution. If ok, check for 12 volts at fuses with ignition switch in the run position. If no good, turn ignition switch to off and test the gray w/yellow trace wire continuity from the fuse panal (fuse #9 or #5) to the ignition switch pin location (A2). If ok, then suspect ignition switch failure...HTH
-- Mike
93 Cobra