Zero electrical power after turning off

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Herewebgoin, Jul 2, 2023.

  1. Herewebgoin

    Herewebgoin New Member

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    2010 Prius
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    2010 Prius
    Everything normal.

    Park, turn power off.
    The entire dashboard IMMEDIATELY goes black.

    That's not normal. Even when you've turned it off, there's normally still some status lights. Dome lights can be expected to work as well as headlights, etc.

    This is dead and no power like dead-dead, and no power as in zero.

    Check the 12v battery, there's no power between the battery posts as long as the battery is connected.
    I.e. looks like a short.

    Wait 30 minutes, everything is fine again. Power is available. Lights turn on, the center console lights up, and the car can start.

    Or sometimes wait forever and it never works again. Hook up jumper cables and everything is ok again. Drive it around, start and stop 30 times, no problem, then it happens again.

    Tested the 12v at garage. Good output. 330 CCA like the battery says.

    Took car to dealership. They sold me a new key FOB because I had inconsistent transmission strength. Then the car continued to fail as before. I.e. it's not the FOB.

    Bought fuses tonight and a voltmeter. Will test battery and fuses tomorrow.
     
    #1 Herewebgoin, Jul 2, 2023
  2. Brian1954

    Brian1954 Senior Member

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    #2 Brian1954, Jul 2, 2023
  3. Herewebgoin

    Herewebgoin New Member

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    Battery is about two years old. For AGM over lead acid, I'm expecting longer service life.
    Charging system for 12v confirmed operational.

    Tested with multimeter. 12v battery seems to show 1.5 volts after sitting overnight, so that supports the theory of a short in the system that is shorting it out.

    Fuses in fuse box all have continuity when I test their top posts.

    I don't have tools to test the solenoids in the relays.
     
    #3 Herewebgoin, Jul 2, 2023
  4. Brian1954

    Brian1954 Senior Member

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    If the 12v battery is at 1.5 volts, it probably is bad.

    I would remove the positive wire from the battery and charge it up. Then take a voltage measurement and then let it sit unconnected overnight and take a voltage reading in the morning. Is the measurement 12.3v or higher?

    FYI. My original 12v battery lasted 9.5 years and I replaced it before it went bad.

    Posted via the PriusChat mobile app.
     
    #4 Brian1954, Jul 3, 2023
  5. rjparker

    rjparker Tu Humilde Sirviente

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    Not really. A short would blow a fuse. A huge parasitic draw might bring it to 7-8 volts overnight.

    Assuming you are really measuring 1.5v the most likely scenario is a loose connection inside the battery. A factory flaw. Depending on the battery temperature or vibration it may work. Remember this battery only supplies a low current for a few seconds during Ready initialization. It may accept many tens of amps if discharged by weeks of nonuse or a much higher than normal parasitic draw. Headlights purposely left on overnight may be the exception. Other significant loads are auto shut off.

    The easy way to verify is to swap batteries. Another method is to measure parasitic draw with a series connected amp meter. 25ma or less after 15 minutes is normal.
     
    #5 rjparker, Jul 3, 2023
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