Electrical Battery Discharging, 92 Lx 5.0

Discussion in 'Fox 5.0 Mustang Tech' started by KW_Pilot, Oct 9, 2013.


  1. KW_Pilot

    KW_Pilot New Member

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    My battery is discharging to the point where I need to start the car every few days. I just bought the quick disconnect from Late Model Resto and disconnected the negative for 6 days while on vacation. The car started but the battery light remained on for about 20 minutes after starting, showing it's still having a good amount of drain even disconnected. The battery is brand new and is a AutoCraft Gold series from Advance.

    Anyone have any ideas?
  2. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Typically it is something draining the battery. Small things like glove box or courtesy lights are often the culprits. If you have an aftermarket stereo or alarm system, it is also suspect.

    The ideal method is to disconnect the negative terminal, and connect a Digital Multimeter (DVM) between the negative terminal on the battery and the negative cable. Set the DVM on a low current scale of 2-5 amps if it doesn't auto range. Watch the current draw, and then start pulling out fuses. When you see a sudden drop in the current, that circuit is the likely culprit. Note that the computer, radio & clock will draw less than 1/10 amp to keep the settings alive.

    Using the negative side prevents nasty accidents like shorting the wrench to ground while disconnecting the battery cable. Electrically, the test will work with either positive or negative battery cable.


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  3. KW_Pilot

    KW_Pilot New Member

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    Thanks man, I'll give it a try this weekend.
  4. fox bodies rule

    fox bodies rule New Member

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    Just to add one item to jrichker's list of common culprits that can drive you nuts is the under hood light, the switch fails in the "on" position.
  5. MFE92

    MFE92 Active Member

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    And if you have ANY aftermarket lighting or stereo equipment, you need to check the wiring and relays for those, because they may not be running through the factory fuse block, and doing amp-drop testing pulling fuses won't find the culprit.
  6. AUBURN1111

    AUBURN1111 Founding Member

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    Just wondering if you ever found the culprit I'm dealing with a similar problem on my 92
  7. Spaz

    Spaz Member

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    Earlier this year I had that and it turned out my hatch was just slightly ajar and my "trunk" light was on. I rarely open my hatch, and after about one week of my battery dying "for no reason" I asked myself what was different than before. I then remembered I got something out of my trunk the week before and voila! problem solved. Hopefully yours is this easy.
  8. KW_Pilot

    KW_Pilot New Member

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    I'm still on the search for my electrical issue. For now, I just ensure I start the car every few days.
  9. Blown88GT

    Blown88GT Founding Member

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    A new battery drained with the negative cable removed from the battery terminal? Only possibilities: battery is bad, alternator is not charging it fully.
    Grabbin' Asphalt likes this.
  10. viper_dude_06

    viper_dude_06 Member

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    I would take the car over to a Super Wal-Mart that has a Tire Lube Express or Autozone and let them hook a tester up to the battery. It will test your Battery, Alternator, and Starter. If the battery is bad it will say bad cell. If the alternator is bad, it will more than likely be an open diode inside the alternator. If your disconnecting the NEG battery cable and its still draining then it has to be the battery. Just cause things are new doesnt always mean they are good. If your leaving it connected then jrichker gave some really good advice.

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