It's sort of the opposite Barry. When you run without lights on, you switch to 'C' which reduces the charge to the battery by half. It's to avoid overcharging the battery, before the days of proper regulators. A common practice nowadays is to convert your 3 brush dynamo to a 2 brush and fit a modern electronic regulator hidden away somewhere. I always recommend. http://dynamoregulators.com/dvr2.php Ron:+1:
Thanks for the info I will get a regulator ordered, how do you convert a 3 brush to a 2 brush. Does it make any difference that the bike still has an old style chloride battery in the rubber/plastic casing on
If it's that original, with it's 3 brush dynamo etc then it looks like you have an unmolested motorcycle from the early thirties. If I had it I wouldn't modernise it at all, just try and keep it as is. There's not many left like that! Some sources quote only 1100 made. After all it was in the middle of the depression era.
It's quite simple If you want to convert it? Which I have done on a couple of Miller dynamos. You remove the obvious third brush and it's holder (if you want) and the cutout (if fitted) which is often mounted to the side of the dynamo. There should be two wires! one from the field winding 'F' and one from one of the two brushes 'D'. These are wired to the corresponding terminals on the regulator F.A.D.E. A= ammeter E= earth.
Some useful stuff here too. http://www.dynamoregulatorconversions.com/2-brush-dynamo-conversions.php
