BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: COBBS on 05 February, 2017, 16:09:54

Title: 1963 C15
Post by: COBBS on 05 February, 2017, 16:09:54
Hi Guys. Please help. My ammeter has not been showing a charge. I have had the stators checked, and the ammeter checked. All Ok. Is it likely that the problem is the rectifier? Unfortunately I know very little about electrics and had the bike with an auto electrician for a month, without resolving the problem.If it is likely to be the rectifier any ideas as to where I could source a new one.
Title: Re: 1963 C15
Post by: JulianS on 05 February, 2017, 16:42:27
What did the auto electrician check and what was his report?

With engine running headlight brightness should increase a bit when you increase the revs meaning there is some output from the alternator.

If not then I suggest you check it yourself before assuming it is the rectifier. It could be other things - the rotor could be low on magnetism after over 50 years, the wiring could be dodgy with poor connections or the switches could be faulty and more.

I would start by checking if there is any voltage coming from the stator - disconnect the 3 cables from the stator from the wiring harness and with a multimeter set on ac volts and engine running check the voltage you get between the cables with the figures between the cables in the attached photo which is from the Lucas service literature.

If you get near the figures from Lucas then the fault could be the rectifier solid state  replacements are available cheaply. See e bay or your favourite classic bike parts supplier.

If no output then you have a faulty alternator. Replacement the solution.

Your C15 from 1963 would originally have had an RM18 alternator and the rotor would have been 74 mm in diameter.
Title: Re: 1963 C15
Post by: COBBS on 06 February, 2017, 05:37:22
Many thanks. That's a big help.