Car won't turn off after installing aftermarket head unit

Discussion in 'Gen 3 Prius Audio and Electronics' started by Tam Nguyen, Jan 22, 2019.

  1. Tam Nguyen

    Tam Nguyen New Member

    Joined:
    Jan 22, 2019
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    Location:
    Dallas, TX
    Vehicle:
    2010 Prius
    Model:
    II
    I replaced my factory head unit with a JVC KW-M740BT head unit recently. I am running into a problem where I have to manually turn on and off my head unit. When I turn off the car, the head unit stays on and all other electronic accessories stay on as well. When I manually power down the head unit, all the other electronic accessories turn off and then my Prius shuts down. What gives?

    Initially, I thought that I mixed up the battery/memory wire with the ignition/ACC wire, but I double checked and I did not mix them up. Why is my head unit preventing my car from turning off? Has anyone else run into this problem?
     
  2. Maarten28

    Maarten28 Active Member

    Joined:
    Jul 13, 2014
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    Location:
    Netherlands
    Vehicle:
    2011 Prius
    Model:
    Three
    I would guess that there is some kind of connection between the always on 12V line and the switched 12V line that causes power to be fed to the car. Try unplugging the new head unit and see what happens.
     
  3. n23

    n23 Junior Member

    Joined:
    Feb 26, 2018
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    Location:
    Tampa, FL
    Vehicle:
    2015 Prius
    Model:
    Persona
    You may not have mixed them up, per a wiring diagram, but maybe the wiring diagram is wrong. My suggestion is to use a multimeter and check line voltage on all the wires with the ignition on and off. I'll bet your switched wire is mistakenly labeled and is actually a constant +12. Plan B, you could run a new switched wire from a known source that does turn off - the power feed to the cigarette lighter for instance.

    Lastly I've heard of circumstances where a large capacitor fed the stereo and amps after power was off. Do you have that equipment in the system too?
     
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