There are no headlight relays. you must replace the headlight and parking light switch located left of the steering wheel on the dash panel. In most cases the wire harness to the switch heat up and burn out. try pulling the switch out. check the harness plug (off white plug) check to see if the plug has a burn mark on the side. I have the same set up in my truck. the lights start flashing when you hit bumps right. I think its a factory defect. I've come accross numerous people with the same vehicle with the same problem. The relay is actually the switch. same concept. the relays on the firewall are for the air conditioning. the relays behind the glove box are for fuel pump and day time running lights i believe