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voltage regulator probs!

Discussion in 'Motorcycle Tech Talk' started by dean s, Jul 27, 2004.

  1. dean s

    dean s New Member

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    just limped back from a shortened road trip with my 91 fatboy after my voltage regulator went on me .repaced it with a new oem regulator and battery ,2days later that one gave up on me I think. still have to check it out when I get my battery charged enough,anyone have an idea what could be causing this???and how I should trouble shoot it? :confused:
    dean s, Jul 27, 2004
    #1
  3. CD

    CD Guest

    Ouch...

    Okay, first check the stator for shorts and output. If it is shorted to ground through either lead or the connector looks like it got hot and melted, replace it. With a multimeter set on AC and 100v rangge connect one lead in each of the stator connector hole being careful not to short to ground. Start the bike and observe the meter. About 15-20 VAC is good at idle and you should see 30-40 VAC at 2,000 RPM. Anyting less indicates a bad rotor or stator.


    Check for proper ground on the regulator mount. If there is corrosion or the ground is bad, it pops the regulator real quick.

    After you fully charge the battery to 13.5 VDC or better (remember, a 12v battery is really a 13.5v battery and less than 12v is dead) do the following.
    1. Measure and note the battery voltage with the switch off.
    2. Start the bike measure and note the voltage.
    3. Raise the RPM to 2,000 and note the voltage. It should be 1.5v or better above the voltage measured in step 2 but I do not like to see higher than 14.8v. The voltage should taper off as the battery approaches full charge to about 13.5-13.8v.
    4. Quickly revving the bike should NOT cause the voltage to spike over 16v.
    If the voltage is less than 1.5v over the voltage in step 2 and the stator checked good check the wire from the regulator to the 30 / 50 amp breaker. If the breaker is good and the wire is good you probably have a bad regulator. If the voltage spikes or is continuously higher than 14.8v the regulator failed in the charge mode. Regulators tend to fail to the open side or the charge side. The charge side is bad 'cause it boils a battery dry, cook stators and the high voltage can damage the other electronics.

    You might want to check over the wiring, do a amp draw test while running and check for draw when all is off. A minor short can add to the regulators load and cause a lot of headaches.

    Get the bible (service manual) out and go for it!:cool:
    CD, Jul 27, 2004
    #2

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