Charge lamp comes on at high rpm

[John Roberts]

As above, bike is an '82 R100RS, it comes on faintly at about 6,500 rpm and over. I've only noticed it after dark with headlamp and two 55W spots on. It's got the Moto Bins high output alternator (400Watts?) fitted. It seems to be charging OK, fortunately, otherwise no other symptoms that I've noticed. Is this normal?

 

[Edward]

I have had a 78 R100 for five years and I have always been able to see a faint glow at night from the charge lamp. I have done nothing about it and the bike has been fine. There are a few threads about it on the BMW club website if you can stand it.

 

[DrFarkoff]

I had a similar problem check the brushes are free moving in the slides and the springs are pressing them down firmly

 

[Kenny]

It is just running at a loss with all those lights on; try it by switching off the extra lighting...if bulb goes out, sorted

 

[John Roberts]

It is just running at a loss with all those lights on; try it by switching off the extra lighting...if bulb goes out, sorted

Yabbut, it only comes on at higher rpm when the alternator is producing (OK: when it is capable of producing) a higher output. Remember, it's got a 400 Watt output, the lights are giving out their full power I'd say, and it charges fine. Having said that I will try it with the spots off, but they are nice to have at over the ton after dark ...

 

[nud1e]

Rectifer board

I'd check the rectifier board for peace of mind. One of the diodes on my R75/6 went short and I seem to remember that the charge lamp started acting funny. Didn't do anything about it until the battery began to lose charge and later the starter solenoid fried.
Rang out the diodes and one was passing current in both directions. New rectifier board solved the problem.

 

[MickDB1]

Get 1 of those 12/24v led voltage do dahs off the bay for about 2 quid or use yer multimeter to determine or proove its voltage output and have a ridearound with it fitted to the battery. Watch where yer going of course. I had a similar problem and it turned out to be the diade board - 1 of the diodes was loose and at a certain frequency it unconnected a third of the output from the alternator
HTHY

 

[DrFarkoff]

John, Any result on this one ??

 

[Wrigsby1]

K's can have the glowing charge light problem... I know the electrics are probably/possibly different but I seem to remember it's down to a build up of crap and corrosion causing resistance in the connectors and especially the one to the charge light... A rash of connector cleaning solved it...

 

[John Roberts]

John, Any result on this one ??

No, sorry, I haven't been out at night on it since my post, I'll keep you posted.

 

[John Roberts]

No, sorry, I haven't been out at night on it since my post, I'll keep you posted.

I just came across this thread again and as I said I'd keep you posted, well, not much to say really other than it's still the same and, happily, still no ill-effects.

 

[jimish]

Yeah. I've had this before too.
Before you spend any unnecessary money clean the alternator slip rings with some meths. Don't mangle your fingers while you're doing it.
Check the alternator brushes are serviceable too and check the slipring wear rate.


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