I've got a strange fault that has started on my G3. When parked without the engine running, the lights and horn all work fine and then suddenly the lights fade to nothing and the horn stops working, like the battery has suddenly been zapped or there is a short somewhere. If I then start the engine, it seems to reset itself and the electrics all work fine again, until the next time it decides to do it. Everything seems peachy when the bike is running, but when stopped it all turns odd. I've checked the wiring, battery, switch, ammeter, all seem fine, and so I now suspect the voltage regulator, any thoughts chaps? It may be worth mentioning that this has only happened since I fitted a brake light and switch, but I cannot see how this would cause such a problem? I hate electrics! I prefer oil, cogs and levers!

For what it's worth you have discribed the exact symptoms as my B33 had, turned out to be the battery I think one of the bridging bars on one of the cells has fractured, when you run the engine the increased voltage and vibration bridges the gap. When I was working as an AA patrol we used to get a lot of this on cars, the car would be dead but if you tapped the side of the battery the power would come back on.

Interesting Ian, it could be just that, thanks for the advice. It's a farily new battery, but I've just had it on charge for 30 minutes and it now all seems much better. Could it be as simple as that? I do hope so.

You find a good number of brand new motorcycle batteries are faulty, so for the price of a new battery it would be worth replacing it if at all suspect

email (option): davmax@ntlworld.com

What sort of regulator are you using ? If it is the mechanical cvc device and the cut-out is not functioning correctly then the battery will not be disconnected from the dynamo and will discharge through the dynamo windings.

Rik, it's all the original hardware, so it's the old mechanical regulator. I've taken the top off and had a good look and it all seems in surprisingly good condition, but I suppose that doesn't really mean much as anything could be going on inside it. I think after what Dave and others have said I'll swap the battery over from my AJS as a test for a start and see what occurs.

Bill, you could also try simply disconnecting the dyno and seeing if the fault still arises.

If you don't have a copy of Radco's "The Vintage Motorcyclist's Workshop" (every home should have one !), there is a copy online on the Norton single site.

https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B_5ev0g65Xk6ZTE0ZmMwNzctMDcwZi00MTk0LWJmMmUtN2Y5NTdkMzg2MTEy&hl=en_US

Have a look at page 178 or thereabouts. It includes some straightforward checks on regulator function.

Thanks Rik, I'll get a copy, knowledge is power. What a great site this is, full of friendly, knowledgable folks. I have no idea when it comes to electrics, but I knew I could rely on you lot, cheers.

Well done everyone, it was the battery, simple as that!! I've replaced it and all seems well again, for now. Cheers lads.