Charge lights are often driven from one winding of the alternator, then turned upside down in voltage by the regulator or instrument panel after detecting a voltage threshold level. No lamp lit (assuming bulb AND wiring ok) usually means no alternator output, a diode stack or regulator faulty.
If the battery connection has been intermittent for a while, this can cause failure of the regulator.
With 100K on an alternator, I'd pull it and check what we said. You can't afford to have an unreliable alternator on these bikes. It's a tow job once the battery runs out. Since you only want to do the job once, you must be certain the alternator you put back is a goer. If BMW stuff wasn't so damn expensive I'd consider exchanging the alternator for a used one off a lower mileage bike or a full serviced one. Not only would you get new brushes, but probably bearings, slip rings, balance and full electrical checks. Alternators can run up to 12,000 rpm!
You could also make a second check putting an ammeter ( at least 30 A) in line with the battery lead but shunt it to start the bike, turn all the lights on and see if it balances the discharge at 3-4K rpm. Because the charge light comes off a separate circuit, you are confirming that the alternator has little or no output. If the charge is balancing the discharge, your problem is in the indication wiring or circuitry.
NEVER run the alternator with the battery leads or ammeter disconnected. You have a 50/50 chance of damaging the regulator, it's also a good idea NOT to hotwire from a cage to start the bike for the same reason. Often you do one or both of these things ending up with more than one component failure in the alternator system.
It's common for regulators to delay and soft charge after first starting to prevent stalling a cold motor on choke.
Never pay again for live sex! | Hot girls doing naughty stuff for free! | Chat for free!