The 6 volt electrical system of the Aermacchi Harley-Davidson Sprint SX from 1971 and 1972 and the SS from 1972, 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 to terminal B+ of the regulator and from there through the fuse to the ignition switch. The negative goes to earth.
Circuit 2ChargingThe generator charges the battery through the regulator. The warning lamp sits between the regulator and the power after the ignition switch.
Circuit 3IgnitionAfter the ignition switch the current goes through the terminal block to the coil. From the coil a black wire runs through the block to the points.
Circuit 4LightingThe switch feeds the dip switch through the terminal block. The dip switch selects high or low beam.
Circuit 5Tail light and clocksThe yellow wire feeds the tail light, also in the park position. The green-black wire feeds the instrument lamps.
Circuit 6Stop lightBoth stop light switches get power after the ignition switch. Either one is enough to light the stop light.
Circuit 7HornThe horn gets power after the ignition switch. The button in the dip switch makes the earth.
BulbsWhich bulb goes whereRating and part number for this model
| Lamp | Rating | Part no. |
|---|---|---|
| Headlamp (sealed beam) | 30/30 W | 67716-68 |
| Tail and stop light | 3/21 cp | 68165-47 |
| Turn signal, if fitted | 21 cp | 68572-50 |
| Turn signal switch lamp, if fitted | 0.6 W | 71088-68 |
| Speedometer lamp, 1971 SX | 3 W | 71093-67 |
| Speedometer lamp, 1972 SS and SX | 1.5 W | 71091-72P |
| Rev counter lamp, high beam and generator warning lamps | 3 W | 71093-67 |
Note: the bulb table gives 3 W for the warning lamps. The key of this diagram gives 1.5 W for high beam and generator. Check what is fitted to your bike. The same key gives 3 W for the speedometer.
From the bulb table in the workshop manual. These are old Harley-Davidson part numbers. cp stands for candlepower, the old unit of light output.
Read this firstWatch out forUncertain colours and terminals
- This is a 6 volt system with a DC generator and a 15 amp fuse.
- Where wires disappear into the loom, the connection was worked out from colour and function. Check those connections with a meter.
- We numbered the terminal block ourselves from top to bottom: 1 yellow, 2 green, 3 green-black, 6 black, 7 and 8 brown. Terminals 7 and 8 are connected.
- Note: the ignition switch terminal numbers differ from the 1970-71 SS. Here: 1 violet (feed), 2 brown, 3 green-black, 4 yellow.
- Switch table in the book: ignition 1-2, ignition and lights 1-2-3-4, park 1-4.
- The dip switch also has a separate wire to earth. Its colour cannot be read.
- This diagram shows only the speedometer lamp.
- High and low beam were worked out from the wire that carries the high beam warning lamp. Check this at the headlamp.
Our own drawings per circuit. The connections are based on the workshop manual for this model. Not an official publication of the manufacturer.