Mysterious short!

[Andreas Larsen]

Hello guys,

I have a mysterious short in the electrical system somewhere and I'm hoping anyone might lead me in the right direction before I lose my patience and buy a whole new wiring harness. 
Right.. I recently converted my A10 to 12V and installed a DV2R in stead of the old regulator. But after I converted it the fuse keeps blowing when I turn on the lights. It doesn't short immediately, I can run a little while and then it goes (some times up to 10 miles).
If I leave the lights switched off, I can step on the brake and get the brake light on with no problem, and I can see that the dynamo charges my battery (this is also the case on the short runs I've managed to do with the lights on before the fuse blows).

First I thought the problem was in the headlight, because the wiring was done really sloppy, so I've rewired what I could in there, but the problem persists.

I run a: 2w speedo light, 5/21w brake/stop, 10w pilot, 35/40w headlight. And the system is +earth. (the regulator is a + earth as well - double checked)
I started out with a 10amp fuse and moved up to a 15amp, but it blows out as well.
And I haven't touched the horn by the way.

Any help is very appreciated!

Andreas

[bikerbob]

I had a similar problem some years ago with a 1957 A10 and it turned out that it was the light switch itself that was causing the problem not the wiring.

[Andreas Larsen]

Ah, alright.. I know the switch has been replaced at some point and I'm not sure it's a lucas one fitted, more likely a cheap replica... Also the person who did it chose to bore three new holes in stead of reusing the original ones... probably because it was a badly made replica..

I might have to buy a new one then.

[warmshed]

The wiring harness around the headstock is always worth a look as it moves with the handlebars, see if it has been rubbing.