BSA Owners' Club Workshop Discussions

The BSA Workshop => Singles => Topic started by: TTJOHN on 10 Apr, 2026, 13:02

Title: C15 elecctrics
Post by: TTJOHN on 10 Apr, 2026, 13:02
Hello
I have a C15G which I have converted to 12v, two wires from the new windings, I have a relay rectifier from Goff two yellow wires feeding with black & red wires coming out which are going to the battery pos & neg connection's, I have changed the ignition switch to a key type so only two connections, I have the normal blue and brown wires going to the ampmeter, Brown & white going to No 3 of the lighting switch. I realise that on the original wiring diagram that there is also a brown & white going too the Zenon diode, which I have done away with. So I am getting a show on the ampmeter discharge when ignition is on, also when lights are on but it does not show a charge when running, although it is clearly charging at the battery. Is there any way to connect so that it is showing the correct rate of charge, any wiring diagrams that show how to connect etc?
All help gratefully received.

TTJohn
Title: Re: C15 elecctrics
Post by: iansoady on 10 Apr, 2026, 14:42
You need to connect the ammeter in series between the regulator output and the battery. Normally one side of the ammeter is connected to regulator and load (lights etc); the other connected to the battery. So take the positive connector from the reg to the battery (assuming negative earth) and attach it instead to the load side of the ammeter.
Title: Re: C15 elecctrics
Post by: TTJOHN on 11 Apr, 2026, 09:44
Ian.
Thanks for that, I'm pos earth, so I should take the lead from the neg side of the battery, I'll give it a go later.
Title: Re: C15 elecctrics
Post by: iansoady on 11 Apr, 2026, 10:27
Not sure if I was clear - take the negative (in your case) wire that you currently(!) have connected to the battery and connect it instead to the load side of the ammeter. It's easy to be ambiguous!
Title: Re: C15 elecctrics
Post by: limeyrob on 11 Apr, 2026, 10:50
At the risk of opening a can of worms. A voltmeter makes more sense with an alternator set up. People fit a small LED voltmeter inside and old ammeter case.
If you stay with the ammeter its (as above) lights, ign and alternator output one side, battery and usually horn and brake light the other.
If its reads backwards just swap the wires.
Title: Re: C15 elecctrics
Post by: Tigerfeet on 25 Apr, 2026, 22:02
I have installed a digital voltmeter in the ammeter hole on my project bike. I have also converted the bike to 12V. The voltmeter is wired in to the headlight feed, on the basis that this was easy to do very late in the project, and I always ride with the headlight on. When I test ran the bike today I turned the light on and was pleased to see 14+V at medium revs - which proves the alternator is working. 
(Piccie is with bike switched off...)