HORN, Horn Wiring Diagram for GMC Pickup C3500 1990, List of elements for Horn Wiring Diagram for GMC Pickup C3500 1990:, (front of right front fender) g101, (left radiator support) g108, Base, Convenience center (left side of i/p), Dual, Fuse block (left side of i/p), Horn relay, Horn switch, Hot at all times, Left horn (below left headlamp), Park lp fuse 20a, Right horn (front of center radiator support), , , COOLING FAN, DEFOGGERS, POWER WINDOWS, HORN, POWER DOOR LOCKS, RADIO, STARTING/CHARGING, WIPER/WASHER, ,