Airhead Charging System Puzzle

Discussion in 'Airheads' started by road2blue, Jul 19, 2004.

  1. road2blue

    road2blue road2blue

    Joined:
    Apr 12, 2003
    Oddometer:
    841
    Location:
    Fraser Valley, BC, Canada
    1993 GSPD with about 85,000 KM (50,000 miles). I just replaced the alternator rotor (for the third time). Prior to and after rotor replacement, I noticed that in the morning I start it up and as I drive the (aftermarket) voltmeter jumps back and forth indicating between 13 and 14.5 volts. It jumps quite a bit which I think is fine - indicates the alternator is putting out power and the regulator cuts in and out as required. After about 10 minutes of riding, the voltmeter needle stabilizes at 13 V. This generally corresponds with my arrival at a freeway on my moring commute. The needle stays pretty much rock solid on my 15 minute highway commute (4500 to 5000 RPM). When I get back into city traffic, stopping for lights,etc, lower RPMs (idle to 4000), the volt meter is indicating only about 11 volts. My total commute time is about 30 -40 minutes. My battery is about 1 yr old and I haven't had a problem with it dying. Could it be a regulator issue that only happens when the bike gets warm? I just added some water to the battery this morning and will keep an eye on it to see if its boiling the acid/water out. My concern is that perhaps my alternator is running full out all the time (once the engine warms up) and that is causing the premature failure of the rotor. I've had the bike since it had about 15,000 km on it (one year old). As stated, I replaced the battery last year (first time) and I've smoked three rotors. Could my regulator or Diode Board be faulty? Currently (pardon the pun), I'm not running any extra electrical stuff (I've got heated grips, vest, radar detector and aux lights but none of these have been switched on since I blew the last rotor and really started paying attention to what is going on). I also haven't done the brushes yet but anticipate updating them before fall/before my next little trip.

    Any help appreciated. Thanks.
    #1
  2. jdiaz

    jdiaz .

    Joined:
    Feb 27, 2002
    Oddometer:
    32,324
    Location:
    Flyover State
    Aren't you supposed to renew the thermal grease on the regulator periodically? I wonder if its not shedding heat correctly and that's causing a problem.

    Jon
    #2
  3. RockyRaccoon

    RockyRaccoon Found:Gideon's Bible

    Joined:
    Jul 6, 2001
    Oddometer:
    63,826
    Location:
    Collapsed in the Corner
    #3
  4. 2UGLY

    2UGLY 2UGLY & 2UGLY2

    Joined:
    Jul 5, 2004
    Oddometer:
    10
    Location:
    Richmond, KY Where Bluegrass Kisses the Foothills
    If you can stand spending the $575.00 for his 400 watt charging system (you get everything new) (http://www.motoelekt.com/charging.htm) you will probably cure all of your "current" problems and have all new parts related to electrical....and be able to run all the accessories you like forever.

    I did it almost 2 yrs ago on my 1990 GSPD and it's the best mod yet! I did a trip to Alaska last summer with heated grips, aux headlamps, GPS, Chatterbox radio, CD/Mp3 player and a 90watt power inverter that runs chargers for digital & video camera batteries and laptop while going down the road (with headlamp on bright ! )

    It works great and I've had no problems. Hope this helps!
    #4
  5. kevbo

    kevbo Rubbery-Lip Flappin' PHI

    Joined:
    May 29, 2002
    Oddometer:
    1,478
    Location:
    Albuturkey
    I'd bet on a flakey diode board. The regulator looks at the voltage coming off a second set of diodes that power only the rotor winding (AKA field, via the regulator). If one (or more) of the main diodes is giving up at temperature, you will be undercharging, and the regulator won't compensate, if _it's_ diodes are fine. Could also be RPM related, as the most common failures are mechanical, and the parts can resonate at particular rpms.

    I don't have a wiring diagram handy, but my airhead came with one in the owners manual. If you can figure out how to monitor the voltage at the second set of diodes mentioned above (the ones that power the field via the regulator) and if it looks good, then it is the diode board.

    Check out the stator windings visually. Stator problems usually show evidence of heat damage to insulation.
    #5