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582 99 regulator issue

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  • 582 99 regulator issue

    I have a radio shack voltage output indicator, and recently have noticed that it is giving out over 15v after start up, although after jiggling the mags and revs it then flicks to normal regulated output. is this a normal trait or the start of complete failure....jc

  • #2
    582 99 regulator issue

    Check the test gear first with a good multimeter.
    If you are getting over 15Volts at any time, check all your earths and then check the regulator by disconnecting it from the aircraft and using a DC power supply on the input terminals, measuring the output with a brake light bulb across it to provide a suitable couple of amps of load. If it then gives fifteen volts, the regulator is duff.

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    • #3
      582 99 regulator issue

      The Rotax regulator doesn't work like that.
      It rectifies the incoming AC and lets each half cycle build to around 14.5v, then it shorts out the rest of the half cycle.
      So the output voltage looks like a sawtooth rising from 0v to 14.5v, then back to 0v.
      This happens 4 times per crank revolution (Bosch) or 12 times (Ducati).
      Obviously, as the load increases, the incoming voltage rise is reduced, so the regulator senses 14.5v and cuts it off later in the half cycle, thus truly regulating the voltage.

      This output waveform, unless smoothed by a battery, or capacitor, is fiendishly difficult for a voltmeter to read accurately.
      So it might just be your Maplin voltmeter. As Tom says, confirm that rogue over-15v with a decent voltmeter - but on the engine, not with a DC power supply.
      If you have electric start, the initial output of the regulator might do odd things as the battery consumes a hefty re-charge.

      On the other hand, it may be a failing regulator, that is correcting itself after a few minutes, or after you jiggle the revs.
      I'd keep a careful eye on your voltmeter, and if it remains over 15v for more than a few minutes, look at replacing it with a Key West.

      Dave

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      • #4
        582 99 regulator issue

        many thanks gents, I am nervous of fiddling with electrics but will try and get another voltmeter in the system. I did replace the unit a few years ago after the battery boiled over. Would you know if Key west units are available in the UK?
        jc

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        • #5
          582 99 regulator issue

          Mark Jones at Galaxy Microlights has Key West Regulators in stock. Just bought one off him last month.

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