The 6 volt electrical system of the Aermacchi Harley-Davidson Sprint SS from 1967 and 1968, 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 the ignition switch. A second blue wire goes to the regulator. 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 to the coil. The points switch the coil, and the coil gives the spark to the plug.
Circuit 4LightingTerminal L of the switch feeds the dip switch, the instrument lamps and the tail light.
Circuit 5Stop lightThe stop light switch gets the blue positive and passes it on to the stop light.
Circuit 6HornThe 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 |
| Speedometer lamp | 3 W | 71093-67 |
| 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.
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 20 amp fuse.
- Where wires disappear into the loom, the connection was worked out from colour and function. Check those connections with a meter.
- In the drawing two blue wires run from the battery into the loom, one through the fuse. Where the blue wires come out cannot be fully traced.
- The names 1 and L on the switch are hard to read in the photo. Check them on the switch.
- On these models green is the power after the ignition switch and blue is the power before it.
- 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.