Motorcycle Repair: Charging System, auto mechanic, flhtcui

Question
I own a 2001 FLHTCUI. Recently I have noticed my alt. gauge swinging. It looks like the system stops charging, and then it begins charging full out. If you do not rev the engine it will charge. But if you speed up, the meter climbs and then stops showing a charge again.
I am a certified Auto Mechanic, could you help me with some diagnostic tests please?
 Thanks
  Benny

Answer
check the battery charge with bike off. now start bike and check again. at idle it should be slightly higher then when the bike was off at battery and as you rev the motor to say 2,500 rpms you should be at at least 14 volts D.C. if voltage is lower  or the same as when bike is not running then you have a charging problem. if all is good then you need to replace the gage. Johnny