The electrical system of the Aermacchi Harley-Davidson M-125 from 1969, drawn circuit by circuit. Each wire is labelled with its colour.
Always check a wire with a multimeter before you connect it, and disconnect the battery first.
Circuit 1IgnitionThe black wire runs from the generator to the coil through the ignition switch. The same wire continues to terminal RU on the handlebar switch. The coil gives the spark to the plug.
Circuit 2LightingThe red wire goes to terminal 51 of the handlebar switch. It selects high or low beam.
Circuit 3Tail light and clocksThe yellow wire from terminal FT feeds the speedometer lamp and the tail light.
Circuit 4Stop lightThe generator supplies the power. The green wire goes to the stop light and to the stop light switch. That switch connects the wire to earth.
Circuit 5HornTerminal T+ feeds the horn. The grey wire goes to terminal T− and the button.
Read this firstWatch out forUncertain colours and terminals
- This model has no battery. The generator feeds the lights directly.
- The inside of the handlebar switch is not shown in this diagram. Check with a meter which terminals are connected in each position.
- The book does not say how the horn button makes its earth. Check with a meter.
- The book does not say which wire is high and which is low beam. Where this page does say so, it was worked out from the warning lamp. Check it at the headlamp.
- Terminals 51 and T+ are joined by a wire.
- Terminals 51 and FT are connected inside the handlebar switch. Check with a meter.
- The ignition switch sits in the black wire between the generator and the coil.
Our own drawings per circuit. The connections are based on the workshop manual for this model. Not an official publication of the manufacturer.