R100RT generator light stays on dimly as revs go up

[Kurt in S.A.]

Just wanted to report to everyone that I did jump the terminals in the plug and the generator light stayed on. It did start dimming slightly as I increased the revs, but the light didn't go out completely and remained fairly bright.

Is this the right observation? I thought that when you bypassed the regulator, you were to watch the voltage output of the alternator at the battery. If the voltage rose rapidly with RPMs, that means there's nothing wrong with the regulator. If the voltage doesn't rise, then you have to continue to look at the alternator and wiring.

Kurt in S.A.

[montmil]

... There's also a little diode on the back of the big board that can couse the light to stay on but you would be charging the battery anyway...

Jean, this is the most interesting line in your post. First time I have ever heard this about the little GEN bulb that generates such a love/hate relationship. I try to maintain any and all info available about its care and feeding.

Might you be able to identify the location and the diode's specifications? That would be most excellent.

[ME 109]

Montmill,

The diode is different to the "gen bulb" located in the instrument cluster.
The diode is located on the rear of the terminal board at the rear of the headlight shell.

To view the diode, simply pull all the wires off the board, extricate the board through the tangled, impossible mess of disconnected wires and there you have it.
PS Take lots of photos.

[ME 109]

Alternatively.................

Here's a pic of the rear of the board.
There's the little sucker at the top right of the pic.

[chasbmw]

Check and clean brushes,

Make sure that they are being tensioned enough by the springs, it's easy enough to get the tension too loose, you will get some charge, in my case enough to get me from Bath to Verdun, when I worked out what I might have done wrong when I was last fiddling with the bike, the solution was easy enough.

[ME 109]

it's easy enough to get the tension too loose

I like that Chas. I'll use it as my new mantra.

[Kurt in S.A.]

I've heard of the diode in the headlight shell but I thought that had a different purpose and is not associated with the charging circuit. Doesn't it have to go with the neutral light and starting in gear as part of the headlight relay? One can add a resistor to the bike's wiring (Snowbum talks about this) which will let the bike continue to charge even if the gen light bulb burns out.

Kurt in S.A.

[Jean]

There's a diode IN the headlight shell, behind the terninals AND another little diode on the back of the big diode board that changes the AC from the alternator into DC to charge the battery.
I think the posts above are going to mislead you, Archie.
The one I'm talking about is behind the big diode board...
ME109's experience is the most likely tho. A bad diode means the alt. output is not all the DC you need...there is an AC component in it that will not contribute to battery charging. TWO bad diodes is even worse.

[ME 109]

I think you're correct there Kurt re the diode.

[montmil]

As the brushes wear down to minimums or below, the spring tension is reduced and battery charging becomes a big "maybe".

I heard a story from a friend of a friend about a "beside the road ghetto fix" that got a frugal Airhead rider going for a wee bit longer while he waited on delivery of his new brushes. Someday, the trick just might get you home.

Guy carved out two tiny wood blocks that fit down into the brush holders and contacted the worn brushes. The wood "shims" added spring tension and the battery had a steady charge rate.

I dunno 'bout this but it does have a slight believability component. YMMV