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September 23, 2014, 02:27:56 PM

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Author Topic: Electriccery  (Read 55 times)


  • Bulleteer
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  • Neil & Buzzy the Bullet
« on: September 22, 2014, 09:45:20 PM »
Hello Fellow Bulleteers:
Last time out, Buzzy stumbled and then died on the road. I thought it was out of gas, but nope - -  the battery had died. I got it home and recharged the battery,  - - runs again but ammeter indicates no charging when the rpms are raised. B u t , when the rpms are raised, the headlight brightens as it should. My question is about the alternator, it seems to be working enough to illuminate the headlight but won't keep the battery charged. If I go on another trip, I'll be running on battery until it wears down again and then stalls. I'm assuming the alternator is fine because it seems to put ac into the headlight to work, but it isn't putting any juice into the battery. Are there separate windings on the alternator for the AC headlight circuit and also for power to the rec. /  reg.? If so, I'll probably have to replace the alternator. I don't want to do that if the trouble is elsewhere. Any ideas as the what the trouble could be.

Neil and Buzzy the Bullet.


  • Grand Gearhead
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  • "But it's a dry heat here in Arizona
Re: Electriccery
« Reply #1 on: September 22, 2014, 10:36:50 PM »
I'm pretty sure the RE's that have a separate AC power to the headlight also have winding's dedicated to producing the AC that goes to the Reg/Rect for the battery and other electrical parts like the points/ign. coil.

IMO, unless the field coils are grossly overloaded, shorted out or a soldered joint fails where the coils are soldered to the output wire, there isn't much that can go wrong with the alternator.

This can't be said about the Regulator/Rectifier.  They get hot doing their job and can suffer internal breaks or just an outright failure of their diodes.

I'm guessing but I think your alternator will have two wires for the headlight/tailight and three (yellow?) wires going to the R/R.
These should be putting out a fairly high AC voltage when the engine is running faster than an idle.  If they are, the alternator is probably OK and the problem is with the RR.
Before you replace the RR, check the 2 output wires right at it.
It may be putting out a nice 13-14 volts DC right at the wires coming out of it but the wiring (or a connector) between it and the battery may be broken or pulled out.

The good thing about replacing the RR is it is usually much less costly than an alternator.
2011 G5 Deluxe
1999 Miata 10th Anniversary


  • Grand Gearhead
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Re: Electriccery
« Reply #2 on: Today at 09:37:25 AM »
R/R does seem like the likely culprit if the battery holds a normal charge.

There is also an AC regulator on the bikes with the AC lighting systems; when this goes it can cause a confusing loss of lighting.  (Obviously not your issue--just noting something that surprised me the first time I encountered it on a friend's bike...)