The electrical system of the Aermacchi Harley-Davidson Z-90 from 1973 and earlier, 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 1Power from the batteryThe positive goes through the fuse to terminal 1 of the ignition switch, and with a red wire to terminal +B of the regulator. Terminals 1 and 5 are joined by a jumper. The negative goes to earth.
Circuit 2ChargingThe alternator supplies the regulator. With the lights on, the switch adds terminals 8 and 9. The warning lamp sits between terminal S and terminal 6.
Circuit 3IgnitionTerminal +B feeds terminal 7 of the switch. With the ignition on, the current goes through terminal 6 to the coil. The other coil terminal goes to the points inside the generator.
Circuit 4LightingTerminal 4 feeds the handlebar switch when the lights are on. It selects white or black to the headlamp.
Circuit 5Tail light and clocksThe yellow wire from terminal 10 feeds the tail light, also in the park position.
Circuit 6Stop lightTerminal 2 feeds both stop light switches. Either one is enough to light the stop light.
Circuit 7HornTerminal 2 feeds the horn. The grey wire goes to the button in the handlebar switch, which makes the earth.
Circuit 8Turn signalsThe relay keeps interrupting the current. The handlebar switch selects one side or the other.
Read this firstWatch out forUncertain colours and terminals
- Switch table in the book: ignition 1-2 and 6-7, ignition and lights 1-2-3, 4-5, 6-7 and 8-9, park 5-10.
- 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 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.
- The negative battery wire has no colour code in the book. That is why it says "colour?".
- This diagram is hard to follow in the photo. Where wires cross, the connection was worked out from colour and function. Check those connections with a meter.
- The wire marked red-black and the black-light blue wire are shown like this in the drawing. Check them.
- On this model the drawing shows no blue earth wire on the handlebar switch.
Our own drawings per circuit. The connections are based on the workshop manual for this model. Not an official publication of the manufacturer.