Hi Anonymous, perform the following tests:
1. Fill acid type batteries to proper levels.
2. Charge battery overnight at 1-2 amps you need 12.5 volts or better after charging.
3. Hook up battery positive cable, then with your multimeter on the milliamp scale connect one lead to the negative battery post and the other lead to the ground cable. Meter should read 3 milliamps or less, 10 milliamps with a radio, 15 milliamps with radio and CB. If your meter reads higher you need to isolate the circuit by pulling fuses and circuit breakers one at a time and observe meter for drop in aprerage then get out your test light and track down the short in that circuit.
3. Make sure all connections are clean and tight especially the negative cable at "BOTH" ends.
4. Hook up volt meter to battery and start engine, if meter falls below 9.5 v while cranking replace battery.
5. With engine running at 3600 RPM battery should read 14.3-14.7 volts if not continue tests.
6. Unplug voltage regulator from alternator at crankcase by front of primary cover.
7. To test voltage regulator go to: https://www.youtube.com/watch?v=F8EjV0IjW9Q
8. With ohm meter, one lead grounded, touch alternator pin meter should read infinity, if not replace stator.
9. With ohm meter, both leads touching alternator pins meter should read 0.1 to 0.2 ohms on 1989 and later models. 0.2 to 0.4 ohms 1988 and earlier models, if not replace stator.
10. With volt meter set on AC scale, both leads touching alternator pins meter should read
16 to 20 volts AC for every 1000 RPM'S 1989 and later and 19 to 26 volts AC for every 1000 RPMS. If not replace rotor.
17. For a free wiring diagram please visit the website below. Good luck and have nice day.
Harley Davidson Wiring Diagrams and Schematics