AJS & Matchless Owners Club

I'm wrestling with a Lucas alternator RM 13/15 three wire 6 volt. The original colour coding on the cables has gone, but I have, using an AC volt meter determined a 'common wire' and a reading of about 6volts on tick over by connecting to the other two in turn. In practice the output is about 4 amps on the road and enough to power the side the lights but no where enough to power the head lamp, staying firmly in the negative of the amp meter. The coils check out and are not shorting to earth, does this sound like a demagnetised rotor? Suggestions appreciated.

You should also find out which wires connect to the low power coil and which to the high power coil. Maybe you can recognize this with resistance measurements; the high power coil (the one with 2 branches in parallel in the schematics) has lower resistance. Between the not-common wires you should read the highest resistance of the 3 possibilities, and also not much AC voltage.
Albert

Sounds very much the same issue as with my G3. It will show a charge with headlight on if speed is over c 45mph, but only just.

Steve

Thanks for the suggestions. I'll get busy with the meter.

Sorry to hijack the thread but I didn't want to start a new one. I've just pulled my alternator off my model 20 and wondered if anyone new if there is a common replacement, as the part numbers have been superseded I think. I'm looking for 6volt to go with my modern rectifier.

The stator

This page is helpful: http://www.aoservices.co.uk/info/ALTERNATOR_COLOURS.pdf

Thanks, I'm looking for a 74mm replacement I think, the current one is 70mm, but these are no longer available

Neil
I believe that the club has these in stock, however it may be an opportunity to consider upgrading to 12v.

Hi
Thanks for the replies. What I want to do is buy a new alternator and I was wondering which one to fit. Te 74mm diameter rotors and matching stator seem to be easy to get hold of, but I don't know which part to get. The old of the stator is 127mm. Is it Rm20 and RM21 I need?