What wire color and circuit number feed the backup lamps?

Circuit 140, a BK/PK (black/pink) wire, carries 12V in reverse from C103 through C202, S232, C205, S254 and C401 to the left and right backup lamps.

What circuit feeds the trailer backup lamps?

Circuit 963, BK/LG (black/light green), is 12V when the Trailer Backup Lamps Relay is energized, running through connectors C149, C424 and C417 to the trailer backup lamps.

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, powered per Power Distribution pages 13-2 and 13-8, and grounded via circuit 57 (BK) through S104 to G100.

Which connectors serve the left and right backup lamps?

Flare Side and All Others use C433 (left) and C434 (right); Chassis Cab uses C447 (left) and C448 (right).

Where are the backup lamp grounds shown?

Ground is circuit 57 (BK) to G100; see Grounds pages 10-1 and 10-7 for the trailer relay branch and page 10-4 for the rear lamp branches through splices S406 and S404.

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Ford Backup Lamps Wiring Diagram 93-3 - Reverse Light & Trailer Relay Circuit

Ford EVTM page 93-3: backup lamps wiring diagram with trailer backup relay and lamps

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Backup lamp wiring diagram showing trailer backup lamp relay and left/right backup lamps for flare side, chassis cab and other body styles.

AI caption July 2018 · Photo 325 of 386

This document is page 93-3 of a Ford factory-style wiring diagram covering the Backup Lamps circuit. It traces circuit 140 (BK/PK wire) from connector C103 (referenced on page 93-1) through connectors C202, C205 and splices S232 and S254, with a branch feeding the Automatic Day/Night Mirrors (page 125-1). A trailer-tow-only branch runs through C149 to a Trailer Backup Lamps Relay inside the Trailer Relay Box, which receives 12V power from Power Distribution (pages 13-2, 13-8) and, when energized, sends circuit 963 (BK/LG) through C149, C424 and C417 to the trailer backup lamps; its ground is circuit 57 (BK) through S104 to G100. From splice S254 the diagram continues to C401 and splits into three body-style variants: Flare Side (via S426, C406, C433/C434 to left and right backup lamps, grounded via S406/S404 to G100), Chassis Cab (via S426 to C447 and C448), and All Others (via S426 to C433 and C434, grounded through S404 to G100). Ground references cite pages 10-1, 10-7 and 10-4. Readers can identify wire circuit numbers, colors, connector and splice IDs, and expected 12V (reverse) test points for diagnosing inoperative backup lamps or trailer backup lamp wiring.

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Frequently asked questions

What wire color and circuit number feed the backup lamps?: Circuit 140, a BK/PK (black/pink) wire, carries 12V in reverse from C103 through C202, S232, C205, S254 and C401 to the left and right backup lamps.
What circuit feeds the trailer backup lamps?: Circuit 963, BK/LG (black/light green), is 12V when the Trailer Backup Lamps Relay is energized, running through connectors C149, C424 and C417 to the trailer backup lamps.
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, powered per Power Distribution pages 13-2 and 13-8, and grounded via circuit 57 (BK) through S104 to G100.
Which connectors serve the left and right backup lamps?: Flare Side and All Others use C433 (left) and C434 (right); Chassis Cab uses C447 (left) and C448 (right).
Where are the backup lamp grounds shown?: Ground is circuit 57 (BK) to G100; see Grounds pages 10-1 and 10-7 for the trailer relay branch and page 10-4 for the rear lamp branches through splices S406 and S404.