What wire colors are used for the headlight high and low beams on the 1979 Bronco/F-Series?

The dimmer switch receives power on a red/yellow (r/y) wire; low beams use green/black (gr/bk) wires and high beams use red/black (r/bk) wires from dimmer switch terminals 2 and 3 to the headlights.

What powers the marker light relay in this diagram?

The marker light relay is fed from Fuse Link F, which is hot at all times (the diagram references page 8 for details).

Which parts of this circuit apply only to F100-F350 trucks?

The shaded 'F100-F350 Only' section includes the marker light relay, the L.H. and R.H. mirror marker lights, and the roof marker lights.

Where do the headlights ground on this diagram?

Both headlights ground with black (bk) wires through splice S807; the L.H. headlight goes to ground G801 and the R.H. headlight to ground G802.

What connectors are in the mirror marker light circuits?

Each mirror marker light circuit passes through connectors C902 and C903 on the feed side and C904 on the ground side, ending at grounds G901 (left) and G902 (right).

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1979 Ford Bronco F100-F350 Headlights & Marker Lights Wiring Diagram

Headlights and marker lights wiring diagram with connectors and circuit paths

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Wiring diagram for the headlights and marker lights showing connectors, grounds, and circuit routing for F100-F350.

AI caption August 2014 · Photo 14 of 48

This document is page 14 of a Ford wiring diagram set covering the Bronco and F100 through F350 trucks, showing the Headlights/Marker Lights circuit. The schematic traces power on a red/yellow (r/y) wire into the headlight dimmer switch (terminal 1), which outputs green/black (gr/bk) low-beam and red/black (r/bk) high-beam circuits to the left and right headlights through connector C801 and splice S801, with a branch through connector C208 or C208A to the high beam indicator light. Headlight grounds run black (bk) through splice S807 to grounds G801 and G802. A brown (br) circuit feeds the L.H. front parking light and L.H. front side marker light. A shaded section marked "F100-F350 Only" covers the marker light relay (fed from Fuse Link F, hot at all times, referencing page 8), the L.H. and R.H. mirror marker lights (through connectors C902, C903, C904 to grounds G901/G902), and five roof marker lights grounding at G909, all connected through C901 and C907. Readers can learn wire colors, connector and splice identifiers, and ground locations for diagnosing headlight and marker light problems on these trucks.

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Frequently asked questions

What wire colors are used for the headlight high and low beams on the 1979 Bronco/F-Series?: The dimmer switch receives power on a red/yellow (r/y) wire; low beams use green/black (gr/bk) wires and high beams use red/black (r/bk) wires from dimmer switch terminals 2 and 3 to the headlights.
What powers the marker light relay in this diagram?: The marker light relay is fed from Fuse Link F, which is hot at all times (the diagram references page 8 for details).
Which parts of this circuit apply only to F100-F350 trucks?: The shaded 'F100-F350 Only' section includes the marker light relay, the L.H. and R.H. mirror marker lights, and the roof marker lights.
Where do the headlights ground on this diagram?: Both headlights ground with black (bk) wires through splice S807; the L.H. headlight goes to ground G801 and the R.H. headlight to ground G802.
What connectors are in the mirror marker light circuits?: Each mirror marker light circuit passes through connectors C902 and C903 on the feed side and C904 on the ground side, ending at grounds G901 (left) and G902 (right).