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Thread: M998 Electrical Woes

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    Sergeant Major
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    Default M998 Electrical Woes

    I've been having some nagging problems with Gunny (my '90 M99. Voltage gauge has been inconsistent and erratic, usually charging, but at times over- or under-charging. So upon inspection, I observed a crack in the VR potting material. I put off swapping the voltage regulator until my batteries were dead. Put new batteries in, and initially, turning on the ignition produced a clicking noise in the ESS box. Subsequently, no click, but also no glow plug light. And no glow plug. Late summer in Texas allows me to start it, but not for long.

    I took every precaution to not fry the box, which I just purchased to replace the burnt up original unit. Any ideas what I'm up against?

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    4 Star General BLK HMMWV's Avatar
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    sure your new batteries fully charged.
    All the grounds good and tight.
    You disconnected batteries before changing out ESS?
    All the connections tight?
    You change out box with same kind you removed?

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    General Katavic918's Avatar
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    Also low batteries are murder on electronics.
    "I feel I was denied.....critical....need to know.....information"

    1970 M35A2 (Sold 8-26-17)
    1991 M998
    1972 M35A2

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    It would be helpful to know what alternator/regulator you have in your truck. Troubleshooting is different for different models of A/Rs. Pictures would be even better!

    Warm weather tells the EESS box that glow plug activity isn't necessary. Something to be aware of because it's the way the system was designed, it's not a problem. Now if it still does it when it's cold you have issues.
    Last edited by papakb; 10-23-2019 at 16:36.

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    I swapped boxes several months ago - it had been working perfectly since. But batteries were low when I experienced the failure. New batteries are charged, connections tight, did everything I was supposed to. If low voltage is bad on the box, that has to be it. Any ideas if the damage is visible? Potential for repair? Another $700 is a tough pill to swallow.

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