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Auxiliary Light Relay Wiring Diagram - 30/85/86/87 Relay, Switch & Two Lights
Reference · 1978-1979 BroncoAll 116 wiring diagrams
Wiring diagram showing two lights powered through a relay (30/85/86/87), an on/off switch, key source, and battery.
Part of 1978-1979 Ford Bronco Wiring Diagrams
This is a simple hand-drawn (computer-drawn) auxiliary light relay wiring diagram, uploaded to a 1979 Ford Bronco gallery. It shows how to wire a pair of auxiliary lights through a standard 4-pin automotive relay (terminals 30, 85, 86, 87). Battery power (BATT) feeds relay terminal 30 via a heavy red wire. An ON/OFF toggle switch is fed from the ignition key circuit (labeled IGN/CON at the KEY symbol) and supplies the relay coil at terminal 85 when switched on. Terminal 86 of the relay coil is grounded. The switched output at terminal 87 feeds two lights (labeled LIGHT), each of which is individually grounded. The battery negative is also shown grounded. A reader can learn the correct relay pinout for adding off-road or auxiliary lights so that the high-current lamp load is carried by the relay directly from the battery, while only a low-current trigger passes through the dash switch and ignition circuit. The diagram is generic and not model-specific, no year, make, part numbers, wire gauges, or fuse ratings are shown.
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Frequently asked questions
- Which relay terminal gets battery power in this light wiring diagram?
- Terminal 30 of the relay is fed directly from the battery (BATT) via a red wire.
- How is the relay triggered in this diagram?
- An ON/OFF switch, fed from the ignition key circuit (IGN/CON at the KEY), supplies relay terminal 85; terminal 86 goes to ground to complete the coil circuit.
- Which relay terminal powers the lights?
- Terminal 87 is the switched output that feeds both lights.
- How are the lights grounded?
- Each of the two lights has its own separate ground connection, shown by ground symbols beneath each lamp.
- Does this diagram show a fuse or wire gauge?
- No. The diagram shows only the battery, relay (30/85/86/87), ON/OFF switch, key/ignition feed, two lights, and grounds, no fuses, wire gauges, or part numbers are indicated.
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