Jumper terminal in fuse box broken

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by newguywithpups, Feb 1, 2025 at 12:31 AM.

  1. newguywithpups

    newguywithpups Junior Member

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    I can't jump my car from the fuse box anymore - have to do it directly from 12v battery in trunk. What exactly might be broken?

    Here's the back story:
    Jumping from the terminal in the fuse box worked fine. One day during a power outage I decided to hook up a power inverter to my Prius. I was too lazy to clear out the trunk to be able to lift the panel and access the 12v battery and connect the inverter to it directly as I'm supposed to. I figured hey this fuse box terminal is for jumping, so it connects to the 12v battery and it must be able to sustain a high current - right? Apparently not. Worked fine for a day but the next day the connection seems to have severed.

    Is there a place the connection is likely (or even designed) to burn out or sever?

    I'd like for the jumping terminal to work, as if there's ever a situation in the future I need to jump the car, I'm sure it'll be the most inconvenient timing to have to clear out the trunk to reach the battery (keeping in mind I won't even be able to open the trunk in that scenario).
     
    #1 newguywithpups, Feb 1, 2025 at 12:31 AM
  2. MAX2

    MAX2 Member

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    The positive wire circuit from the 12V battery runs under the bottom of the car to the engine compartment. It is unlikely to have broken. The problem may be a fuse that has blown due to improper connection or high load.
     
    #2 MAX2, Feb 1, 2025 at 12:43 AM
  3. newguywithpups

    newguywithpups Junior Member

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    Yeah I figured the line running to the fuse box didn't sever since the rest of the circuits and the car in general seems to run fine. But what fuse would there be? The red jumper terminal in the fuse box looks to just be a connection point with no fuse. Maybe it's actually fused somewhere? I guess I can pull and check every fuse (I forget if I can check the fuse without pulling it, but whatever, point is to check all the fuses)?

    I ran the inverter for several hours just fine, at times drawing enough current to run a space heater so I figured that would instantly blow any of the fuses if that connection were fused. But I guess I'll check fuses anyway...
     
    #3 newguywithpups, Feb 1, 2025 at 12:57 AM
  4. MAX2

    MAX2 Member

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    So you are saying that the car starts as usual and works?
    But 12V power only comes from the battery to the fuse box and nothing else. At the terminal under the cover, this voltage is either present, and then the car starts, or not, and the car does not start.
     
    #4 MAX2, Feb 1, 2025 at 1:12 AM
  5. xliderider

    xliderider Senior Member

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    Easiest way to tell is measure the voltage, or lack thereof at the jumper terminal.

    You do realize that only one side of the jumper terminal is copper, right? Sometimes the clamps that come with some jumper cables, etc are only connected to one side of the clamp's jaws.

    SM-G781V ?
     
    #5 xliderider, Feb 1, 2025 at 1:24 AM
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  6. Tombukt2

    Tombukt2 Senior Member

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    Clamps are all like that generally been waiting for this . I never use that jump point ever it looksike a weak point . I have an extension at rear tray penetrating that lid so access is easy w full trunk for jump. But we e never had to use . It's only to get travelers out of our way if needed.
     
    #6 Tombukt2, Feb 1, 2025 at 7:22 AM
  7. ChapmanF

    ChapmanF Senior Member

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    I second #5. What does a voltmeter or test light from that jump terminal to ground say when the car is off?
     
    #7 ChapmanF, Feb 1, 2025 at 2:56 PM
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  8. newguywithpups

    newguywithpups Junior Member

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    Thanks everyone! Sorry I haven't tried any of the suggestions yet. Lent someone the car and they ran into some issue with snow chains and now I can't even pop the hood (among a handful of other problems). Will take it to a mechanic to be fixed then will continue troubleshooting the jumper terminal (or maybe I'll just ask the mechanic about that, sigh lol).
     
    #8 newguywithpups, Feb 2, 2025 at 7:14 PM
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