Ford Bronco/F-Series Backup Lamps Wiring Diagram 93-4 - Trailer Relay & C433/C434

This document is page 93-4, "Backup Lamps," a factory-style wiring diagram covering the backup (reverse) lamp circuit. Power arrives on circuit 140 BK/PK, energized at 12V in reverse. A branch labeled BRONCO feeds the Trailer Relay Box (referencing Power Distribution page 13-2), where circuit 37 Y (12V) and circuit 140 BK/PK operate the Trailer Backup Lamps Relay, which "directs current to operate trailer backup lamps." When energized, the relay outputs 12V on circuit 963 R/Y through connectors C149, C424, and C417 to the trailer backup lamps; the relay grounds through circuit 57 BK via splice S102 to ground G100 (see Grounds page 10-1). The vehicle backup lamps split into two configurations: Chassis Cab uses splice S426 feeding connectors C447 (left backup lamp) and C448 (right backup lamp) on circuit 140 BK/PK; All Others uses splice S426 feeding connectors C433 (left) and C434 (right), with lamp grounds joining at splice S404 to ground G100 (see Grounds page 10-4). A reader can learn wire circuit numbers, colors, connector identifiers, splice points, ground locations, and how trailer backup lamps are relayed on Bronco applications.