Please, Al Osborne, can you give me the Roadholder issue number where you explained how to test an alternator? I can't lay my hand on it.
Michel, spoke to our electrical guru this afternoon, he will come on later and explain!
To Test the rotating magnet (RM) type alternator as we have on our Nortons.
Static test- with a multimeter - check for continuity between all wires, two/three. There should be approx 1-2 Ohms resistance. A three phase (9 pole pieces) will have the same resistance between the 3 wires while an RM19 (6 or 12v usage) will have a slight difference between the wires. Then check between any wire and the metal of the alternator (or earth/metal of the engine if alternator is still on the bike) there should NOT be any connection. This should be a good one.
Dynamic test- On the bike. (slightly more useful test) Prepare a 12V headlamp bulb with wires to one filament (and perhaps a pair of clips). Disconnect the alternator wires from the bikes wiring, connect the lamp across any two wires. Start the engine. At a fast tickover there should be a bright light. (Change the lamp to another combination if you have three wires, check you have output using all three wires). Disconnect one lamp lead and connect it to earth-metal of the bike. There should NOT be any light. This would be a good working alternator.
Full Output test-If you are reasonable conversant with the use of a multimeter on Amps, this is what you can do. Remove the output lead of your rectifier or regulator/rectifier and place you meter on 10 Amps DC between the lead you have pulled off and the rec/reg output. Start the bike. Put all the lights on. By revving the engine you should get up to 9 Amps from an RM19 or RM21. The MKIII high-output (RM23) should go up to nearly 14 Amps but of course awkward to measure but you should pass the 10 Amp below 3000RPM. Any reduced output is most likely due to tired magnets if the rotor is over 5 yrs old. You might have lost some windings though if you are over 1/3 down.
Have fun. (nice one Gino-Hope this helps Michael)