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please help! motor cycle fault finding

Discussion in 'Sensors and Actuators' started by marcanthonysiphone, Mar 21, 2010.

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  1. marcanthonysiphone


    Mar 21, 2010
    im trying to track down a short on my harley. well i think its a short, somewhere i read that if you disconnect the neg from battery and use a test light as a jumper for the neg and if the light glows you have a short... is this true? what i get is a small glow through it when key is on, and than when i turn the key 1 more click for the lights to come on, it glows really bright. is this right or is something wrong?

    Thank you all whoever takes the time and reads or answers
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    I'll hazard a guess that your hog has an electric starter. When it glows really brightly, that's probably the cause :)

    First things first though. Why do you think you have a short?
  3. marcanthonysiphone


    Mar 21, 2010
    yes it does have an electric starter.... I think i have a short cause if i let it sit for more than 1 day the bike wont start w/out help. So i thought somthing is draining the battery after its shut off. Now the battery is toast but im not gonna replace it till im certain ive found and fixed the prob or certain everything checks out ok. i think the voltage regulator is bad now after doing mor trouble shooting and testing. thanks again for your input:)
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    OK, you don't have a short. If you had a short you would have much more dramatic things happening, probably involving blown fuses or smoke.

    It sounds like you have a battery with a dead cell, or something using current when the switch is otherwise in the off position.

    I would recommend (if you can) disconnecting the battery for a day or so and seeing if it still starts when you reconnect it. If it does, then you have something using power when the bike is "off", if it doesn't, it's time for a new battery.

    A third alternative is that the battery may not be being charged correctly, but I think that's a distant third.
  5. marcanthonysiphone


    Mar 21, 2010
    Ok i can kinda stop stressing over it than. Yes something is drawing power when its off, its the voltage regulator, if i disconnect the voltage reg and use multimeter as a jumper for negi have all zero's when the key is off. With the voltage reg plugged in i get 1.65vdc when the key is off. So the voltage reg is shot than. Other tests ive run on the reg indicate its bad if im doing them correctly. thanks again...
  6. listener85


    Mar 23, 2010
    Bike wiring

    OK, just because you can read a voltage from your bikes neggy battery terminal to ground doen't mean you have any significant current flow, or that the regulator is necessarily at fault.

    I would suggest that you set the meter to a current range.... start at 10A DC to be on the safe side, and put that between the negative battery terminal and ground. With the bike ignition switched on you may get a few amps flowing depending on your ignition circuit, but with it switched off there should be little or nothing flowing. If nothing shows, switch to a more sensitive range (say 200mA DC) and check again (with the ignition off).

    If the bike has an alarm, an electronic regulator, or anything else that still works when the ignition is off, some current will be drawn, but I wouldn't expect it to be more than maybe 20mA if there is an alarm on the bike, or less than 5mA if there isn't.

    All of this assumes you have a charged battery of course (or clip a battery charger across the battery while you do the tests.

    So, if there is some significant current flowing when the ignition is off, then something isn't right.... that might be the regulator, or it may be something connected downstream of the regulator but before the ignition switch, in which case you have to track it down by using the bike wiring diagram and tracing and disconnecting connectors that feed anything before the switch.

    I hope thats of some help. Don't go by voltages, especially using an electronic meter, they can read a voltage when virtually no current is flowing and that can only mislead you. However, do be VERY careful not to pass too much current through your meter on a sensitive amps scale and under NO circumstances put a meter set to current across the battery terminals, or between the positive battery terminal and anything connected to the bike chassis/ground. If that wasn't already obvious, the meter going "pop" and dying would make it so.
  7. 55pilot


    Feb 23, 2010
    My advice to you is that when you hear hoof-beats, think horses, not zebras! Right now you are chasing zebras and unicorns.

    The simplest explanation for your problems is a bad battery. How old is the battery?

    Replacing the battery would be a lot easier and cheaper than replacing the voltage regulator or alternator and much much much simpler than chasing a non-existent current drain. Change the battery and see if that fixes it. If not, then we will figure out the next step.

  8. sall


    Jan 29, 2010
    Load test the battery. Even if it holds a charge it does not mean it's CCA are up to par. If it fails get a new one. They do this for free at Advance/AutoZone.
  9. Steelie


    Mar 25, 2010
    Hey can't help with this although I am usually good at bikes.
    Go to thebikerforum and ask there, click HERE
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