Does it only happen when the headlight switch is on? Could be the headlight switch dimmer that regulates the dash lights. If it does it without the headlights on, start with the door pins and work your way back on the wiring as something may be rubbing. Also, if you don't use interior lights that much and want to wait on repairs, pull the bottom right 10 amp fuse behind the glove box. That fuse is for interior lights.