More than likely the portion of your multifunction switch for the headlights and brights has failed. I had this problem in my 91. I went under the dash and removed the wiring input for the headlights. I just wired mine straight from the switch to a relay that I tapped off the alternator. I did the same thing with my fog lights, so the switch turns on a relay and the power passes from the alternator to the lights. The relays are available for about $5 each at any auto store. You can order parts from LRS to properly repair the issue, you will need a new connector and switch I think it will run you about $90. I would still split off my fog lights on a relay, since this is probably the root cause of the problem.