What feeds the 'S' terminal on the start relay in this diagram?

A '12v Start Only Source' feeds the S terminal of the START RELAY.

How is the ignition relay triggered in this diagram?

The IGN. RELAY 'S' terminal is fed by a '12v Key on Source', and its 'G' terminal is wired to chassis ground with a black wire.

Where does the starter get its power in this diagram?

The STARTER is fed from the output side of the START RELAY, which receives power from the battery positive terminal.

How is the battery connected in this diagram?

The battery negative (-) terminal goes to chassis ground and the positive (+) terminal feeds the START RELAY power terminal, which also ties into the ignition relay circuit.

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1985 Ford Bronco Ignition & Starter Relay Wiring Diagram - Battery to Ignition

Start relay and ignition relay wiring diagram with battery, starter and 12V switched sources

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User-drawn wiring diagram showing start relay and ignition relay connections: battery to start relay (12V start-only source) and ignition relay (12V key-on source) feeding starter and ignition.

AI caption April 2019 · Photo 1136 of 2004

This is a simple hand-drawn (computer-drafted) wiring diagram, uploaded as "Ignition Diagram.jpg" for a 1985 Ford Bronco, showing a two-relay starting and ignition circuit. It depicts a BATTERY with its negative terminal grounded and its positive terminal feeding a START RELAY. The start relay has an 'S' (signal) terminal fed by a "12v Start Only Source" and an 'I' terminal; its output feeds the STARTER. A second relay, labeled IGN. RELAY, has an 'S' terminal fed by a "12v Key on Source" and a 'G' terminal wired to chassis ground via a black wire. The ignition relay's power side ties into the battery/start relay feed and its output goes to a box labeled IGNITION. The diagram uses red lines for power wiring and black lines for grounds. No wire gauges, colors codes, part numbers, fuse ratings, or year/model applicability are stated in the drawing itself. A reader can learn the basic relay-based hookup scheme for powering an ignition system from a key-on source and cranking the starter from a start-only source, typical of Ford-style external starter relay wiring.

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Frequently asked questions

What feeds the 'S' terminal on the start relay in this diagram?: A '12v Start Only Source' feeds the S terminal of the START RELAY.
How is the ignition relay triggered in this diagram?: The IGN. RELAY 'S' terminal is fed by a '12v Key on Source', and its 'G' terminal is wired to chassis ground with a black wire.
Where does the starter get its power in this diagram?: The STARTER is fed from the output side of the START RELAY, which receives power from the battery positive terminal.
How is the battery connected in this diagram?: The battery negative (-) terminal goes to chassis ground and the positive (+) terminal feeds the START RELAY power terminal, which also ties into the ignition relay circuit.