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Random Voltage spike

Discussion in 'Wrangler TJ Builds (1996-2006)' started by Raven Gray, Nov 20, 2021.

  1. Nov 20, 2021 at 2:56 PM
    #1
    Raven Gray

    Raven Gray [OP] Member

    Joined:
    Apr 23, 2021
    Member:
    #5568
    Messages:
    11
    Vehicle:
    97 TJ 2.5 Lil Dog
    Recently I've been getting a "check gauges" warning shortly after starting the engine. The warning is for the battery voltage gauge. It is spiking to 19vdc. I'll shut off the engine and restart, typically the gauge returns to the normal 14+- operational voltage. A test on the battery itself shows normal full charge voltage. That said, I've never had the multimeter handy when the dash gauge reads 19vdc nor have I checked the alternator.
    Before I dive in and start checking all the connections. Has anyone else had a similar experience and advice on what/where to focus my attention? I have been driving on some very dust and rough washboard roads. The temps are not overly hot mid 70-80f.
    Any ideas would be appreciated. Thanks
     
  2. Nov 20, 2021 at 9:43 PM
    #2
    aggrex

    aggrex Well-Known Member

    Joined:
    Sep 12, 2016
    Member:
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    DE
    Vehicle:
    Backcountry '16
    Tuffy>AEV>TTO>JW>STech>EVOcage>MagnaFlow>SpiderTrax>RockHard>TF>SpringTail>67design>Bolt>GPCA>Curt>
    Local auto parts stores like Advance/Autozone can check the battery/alternator charging system.
     
  3. Nov 21, 2021 at 6:37 AM
    #3
    Raven Gray

    Raven Gray [OP] Member

    Joined:
    Apr 23, 2021
    Member:
    #5568
    Messages:
    11
    Vehicle:
    97 TJ 2.5 Lil Dog
    Unfortunately I don't have that option. Nearest auto parts store like that is two-three hours away. I hoping to find some "home diagnosis" options. Some "backyard voodoo jeep repair" ideas. :)
     
  4. Nov 21, 2021 at 7:11 AM
    #4
    aggrex

    aggrex Well-Known Member

    Joined:
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    Member:
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    Messages:
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    DE
    Vehicle:
    Backcountry '16
    Tuffy>AEV>TTO>JW>STech>EVOcage>MagnaFlow>SpiderTrax>RockHard>TF>SpringTail>67design>Bolt>GPCA>Curt>
    Get a multimeter to confirm the battery voltage versus dash gauge. Generally the battery should read approx 12.6V before starting and range 13.7-14.7 running. Based on the age of the Jeep the cables and connections should be inspected/cleaned from end-to-end for corrosion/decay. Usually bad grounds can cause crank-no starts or intermittent/poor charging but it's not often pumping out 19V unless the alternator is on its way out
     
  5. Nov 21, 2021 at 9:35 AM
    #5
    Raven Gray

    Raven Gray [OP] Member

    Joined:
    Apr 23, 2021
    Member:
    #5568
    Messages:
    11
    Vehicle:
    97 TJ 2.5 Lil Dog
    As mentioned in the original post the battery is good both in a standing 8hr measurement (12.68vdc) and 13.8vdc under a running charge but I can't test battery performance under load. A couple of new observations. The ECM only shows a code 12. Which could correspond to a couple months ago when I had the battery fully disconnected. (Jeep has not been started more then fifty times since then and before anyone asks, I have checked the terminal connections. They're clean and good.
    That said this AM when I started the Jeep up, it spiked, I turned it off. Reread the battery voltage. It was down to 12.5 but recovered quickly, restarted the engine, no new spikes charging at 13.7vdc I didn't notice it at the time but while driving down the road I saw the radio had reset the time to 12:00am. Sooo, at some point it thought there was a total loss of current. I think that would lead to your 'loss/dirty connections. Just not sure where to start looking. At the ECM, at the alternator, at the power control module, all of the above?
    Did I also mention i hate electrical issues?
     

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