Question about Harley Davidson Harley-Davidson Motorcycle Desktop Telephone

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Battery draining down setting in the garage.

I have 1996 HD ultra classic. The battery keeps going down setting in my garage. I have replaced the regulator and the battery in the past year and it does the same thing. I have checked for an open circuit and can't find anything. On the road the gauge says that it is charging about 12 volts. I just don't understand and can't figure it out. Thanks

Posted by abbysgrandad on

  • shelly_fine2 Aug 12, 2008

    ig nition switch was it doesnt charge the battery.

  • abbysgrandad Aug 14, 2008

    Thank you I will check using your suggestions.




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Posted on Jan 29, 2009



Disconnect regulator, insert one ohm meter lead into any hole on plug from alternator and the other to ground, the reading should be no continuity, if it does then there is a ground in the stator, needs replacement. remove ohm meter lead from ground and insert into other hole on alternator plug, resistance should be .2 to .4 ohms (pretty hard to read) but if resistance is lower, stator is damaged and needs replacement. at about 2000 rpm the ac voltage should be around 38 to 52 volts. if out of spec's could be a faulty stator or rotor(highly doubt it but things can happen such as magnets loosing their flux). if in spec's make sure regulator has a very good ground. there are other tests that can be done to check regulator but since it was changed i would say you are "ok" but murphy's law can still have an effect. make sure you are not overloading the system because if you take out more than you are putting in, the battery has to make up the short fall. the other poster is simply wrong, why would harley put out a bike with no charging system, by the way, the so called magneto system he refers to went out at the end of the sixties when the *** bikes showed the americans how to do it with permanant magnet alternators!

Posted on Aug 18, 2008



Yes they do have an alternator, do not know where you've been living. i have too many bikes and i did type in some misleading info, that was for a yamaha. the harley output from the alternator is 30 to 50 volts ac current(not dc as in a generator) on the two wires coming from the stator ring(rpm dependant) and is rectified to dc by diodes in the regulator. harley coils are wired to output on two wires and not 3 phase like some bikes. being permanant magnet design makes for no need for excitation current, that is why you can push start the beast with a dead battery. if you need detailed info, leave address and i will get back between work. when you say magneto i hope you are not talking about ingition, even lawn movers have a so called magneto charge system (ac) rectified by diodes usually with no regulator because the coil output is designed for fixed output. need info on mag ign, i got that too.

Posted on Aug 17, 2008


Harley alternator not charge up a battery, i do not think so. the harley alternator is usually a pretty good unit however like anything problems will arise. you have ruled out the regulator and battery by changing them but you need to look at the alternator itself. this should be a permanet magnet design where the magnets cross over several coils of wire thus producing electricity. i doubt seriously the magnets are bad so look at the coils. you can check them with the plug disconnected from the regulator with a volt meter. you will have a ground and three wires that will produce voltage. this will be an alternating current with the bike running. if you have one that is not producing, then you have a problem with one phase of the alternator. this will reduce amperage output and this will cause the battery to slowly draw down. remember too that if you exceed the amperage output with accesseries then the battery will slowly go down also. if you have to replace the coil ring, go aftermarket with a higher output unit, i think accell makes one. when riding, the voltage should be 13.8 to 14.2 ideally on your guage.

Posted on Aug 14, 2008

Ryan Rogers

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You've got something that's pulling from the battery. It could be as simple as a loose connection or bare wire touching the frame, it could also be a bad relay, but this would generally show when testing for an open circuit. Check any added electrical devices. Also, keep in mind that the system on a Harley doesn't charge the battery, it only keeps it topped at where it's at. So, if you have a half charge on the battery, you can ride to Hawaii and back, and you'll still only have a half charged battery. This is where a battery tender comes in helpful for garage time. I'm afraid you're just going to have to start tracing wires. I ride a 95 Softail, did a harness trace last winter while waiting for new paint, and was amazed at the amount of wear the wires had. Ended up running about 30 feet of new wire to replace weak, worn, and exposed.

Posted on Aug 12, 2008

  • Ryan Rogers
    Ryan Rogers Aug 14, 2008

    Well guest, first off Harley's do not have an alternator, it's a magneto system, and magneto systems do not charge, they provide power to the bike and only keep the battery topped off. The only way the system will charge is if you added a generator, or have an older, mid 70's model. Some of the AMF bikes came equipped with a generator system.


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