JD GT235 Electrical issues

Discussion in 'Mechanic and Repair' started by csblunt, Sep 3, 2007.

  1. fixer67

    fixer67 LawnSite Silver Member
    Messages: 2,098

    This can explain better than I can


    Some meters will read a DC voltage even though the meter is set to AC. A meter that reads TRUE RMS AC VOLTAGE when set to AC will so no voltage when a DC voltage is applied. The meter looks for the voltage swing and AC voltage swings (cycles) and DC voltage does not. The words TRUE RMS will show up somewhere on the box or paper work for the meter. Use a GOOD name brand meter like Fluke and you will be OK. A lot of the cheap off brand meters are not TRUE RMS meters. And a cheap meter can not see a AC voltage riding on a DC voltage. Trust me on this one I have learned the hard way. When you are looking for a DC and AC voltage on the same line you need a meter that can tell the two apart. Lets say you have a 12 volt DC and a 20 volt AC on the same line. You set a cheap meter that is not TRUE RMS on AC it will read 20 volts AC but set it to DC and it will read 20 volts DC. OK lets say the voltages are switched and now you have 12 volts AC and 20 volts DC on the same line. The cheap meter will show 20 volts AC even though the AC voltage is only 12 volts and it is the DC that is 20. I have learn this the hard way.
  2. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 964

    So just EXACTLY WHERE on that link does it back your claims?
    One statement it made was "DC voltage is constant."
    Anybody working on charging systems on small engines, that are only equipped with a diode, knows that you are getting a PULSATING DC!
    AC means the voltage ALTERNATES between negative and positive.As long as it meets those requirements, it's AC. IT DOESN'T HAVE TO BE A PURE SINE WAVE!
    With this posters system, who knows what kind of AC waveform may be present! It may be going 2V positive and 30V negative. It may be "spikey", sawtooth, sinusoidal or some combination thereof!
    The point is that it's AC and therefore has a negative component. The negative part is going to try to "reverse charge" the batter to some degree.
    A cheap meter will show that there is an AC voltage and that's what matters. It doesn't matter how PURE the AC waveform is.
    I'll trust myself on that!
    Google "Sea Tech Transmissometer". Guess who built them for 16 years?
  3. csblunt

    csblunt LawnSite Member
    Messages: 4

    Well I had to order the Voltage Regulator from the local JD dealer as they didn't have any in stock. I picked it up on Saturday and replaced the battery as well since it wouldn't hold a charge even after putting it on trickle charge for 24 hours (just kept dropping from 12.7 to around 6 volts anytime a load was put on it). Everything seems to be working now - charging system is keeping battery at around 14V and everything seems to be in order now.

    Thanks for all of your feedback and help!


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