What wire circuit powers the Ford Bronco backup lamps in this diagram?

Circuit 140 BK/PK (black/pink), which carries 12V when the vehicle is in reverse, feeds the backup lamps through splice S426.

What does the Trailer Backup Lamps Relay do?

Per the diagram callout, it directs current to operate the trailer backup lamps. It is located in the Trailer Relay Box, is fed 12V by circuit 37 Y from Power Distribution (page 13-2), triggered by 140 BK/PK, and outputs 12V (relay energized) on circuit 963 R/Y through connectors C149, C424, and C417 to the trailer backup lamps.

Which connectors serve the left and right backup lamps?

On Chassis Cab vehicles: C447 (left) and C448 (right). On all other vehicles: C433 (left) and C434 (right).

How are the backup lamp circuits grounded?

The relay grounds through circuit 57 BK via splice S102 to ground G100 (see Grounds page 10-1). The 'all others' backup lamps ground through splice S404 to G100 (see Grounds page 10-4).

What wire color is circuit 963 to the trailer backup lamps?

Circuit 963 is R/Y (red/yellow) and carries 12V when the trailer backup lamps relay is energized.

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1996 Ford Bronco Backup Lamps Wiring Diagram 93-4 - Trailer Relay & Grounds

Ford 93-4 Backup Lamps wiring diagram with backup lamp switch, trailer relay box, color-coded circuits

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Wiring diagram for backup lamps showing chassis cab and trailer backup lamp relay circuits with color-coded wires and connectors.

AI caption July 2018 · Photo 331 of 386

This document is page 93-4, "Backup Lamps," from a Ford wiring diagram manual, showing the reverse (backup) lamp circuit. Power arrives on circuit 140 BK/PK (black/pink), which carries 12V when the transmission is in reverse. A branch labeled BRONCO feeds the Trailer Backup Lamps Relay inside the Trailer Relay Box; the relay coil is grounded through circuit 57 BK via splice S102 to ground G100 (see Grounds page 10-1), and its 12V feed comes from circuit 37 Y (yellow) from Power Distribution page 13-2. When energized, the relay outputs 12V on circuit 963 R/Y (red/yellow) through connectors C149, C424, and C417 to the trailer backup lamps. For the vehicle's own backup lamps, two body-style branches are shown: CHASSIS CAB (circuit 140 BK/PK through splice S426 to connectors C447 left lamp and C448 right lamp) and ALL OTHERS (splice S426 to C433 left backup lamp and C434 right backup lamp, grounded via splice S404 to G100, see Grounds page 10-4). The diagram documents all wire circuit numbers, colors, connector IDs, splices, and grounds for troubleshooting backup lamp problems.

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Frequently asked questions

What wire circuit powers the Ford Bronco backup lamps in this diagram?: Circuit 140 BK/PK (black/pink), which carries 12V when the vehicle is in reverse, feeds the backup lamps through splice S426.
What does the Trailer Backup Lamps Relay do?: Per the diagram callout, it directs current to operate the trailer backup lamps. It is located in the Trailer Relay Box, is fed 12V by circuit 37 Y from Power Distribution (page 13-2), triggered by 140 BK/PK, and outputs 12V (relay energized) on circuit 963 R/Y through connectors C149, C424, and C417 to the trailer backup lamps.
Which connectors serve the left and right backup lamps?: On Chassis Cab vehicles: C447 (left) and C448 (right). On all other vehicles: C433 (left) and C434 (right).
How are the backup lamp circuits grounded?: The relay grounds through circuit 57 BK via splice S102 to ground G100 (see Grounds page 10-1). The 'all others' backup lamps ground through splice S404 to G100 (see Grounds page 10-4).
What wire color is circuit 963 to the trailer backup lamps?: Circuit 963 is R/Y (red/yellow) and carries 12V when the trailer backup lamps relay is energized.