charging system

Discussion in 'KJ General Discussion' started by belvedere, Aug 8, 2019.

  1. belvedere

    belvedere Full Access Member

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    Oct 23, 2008
    Our 06 Liberty 3.7 is not charging the battery. Connections are tight and clean, and the belt is in good condition and tight. I know that it's almost certainly the alternator, but that it could possibly be the PCM (which contains the VR). Can someone tell me the test procedure to pinpoint whether it's the alternator or PCM/VR? Thanks!
  2. Billwill

    Billwill Full Access Member

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    Nov 26, 2009
    White River, South Africa
    I posted a reply here a while back on this not know if it was to you!

    The thick lead that goes from the Positive post of the battery to the large Lug on the alternator carries all of the heavy charging Amps.

    With the Engine and ignition OFF measure the voltage on this thick cable at the battery negative post with respect to engine/ground. Should be +12 volts obviously. Now measure this at the thick lug on the alternator...should also be +12 volts as it is the same lead.

    However this thick lead is known as a "fusible link" ie. it has a fuse built into it that blows due to a short to ground. If that +12 volts is not there then you need to buy a new "fusible link" for that model Jeep.
    Disconnect the battery leads completely before removing this link..this link often gets blown by the end of your wrench shorting to chassis/engine while tightening/loosening the connection at the battery post.
    LibertyTC likes this.