BMW K 1100 LT/RS - Manual (Page 108)

12.22
Troubleshooting
Troubleshooting on alternator
Alternator makes noises.
Do carbon brushes whistle? yes
Rework slip rings/replace carbon brushes.
Battery produces excessive gas (vapour)
no
Check contact between regulator/alternator
and between alternator/diode carrier.
Is contact poor?
yes
Repair cable connections.
no
Check regulator.
Is regulator defective? yes
Renew regulator.
no
Check battery.
Is battery defective? yes
Renew battery.