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Instrument Panel Lights adjustment

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Fivel, Oct 16, 2020.

  1. Fivel

    Fivel Junior Member

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    Vehicle:
    2007 Prius
    Model:
    Base
    Hi all,
    I can't adjust the instrument panel lights on my 2007 base Prius. I just got the car in June, the adjustment hasn't worked the whole time I've had it. The combination meter and other dashboard lights all work fine, but I can't adjust them — the adjustment knob does nothing, neither reducing nor brightening the lights. Also, the lights on the steering wheel, around the MFD, etc., never come on.

    Given that the combo meter works, it hasn't been an real issue, but I'd like to look into getting this working. Thoughts on how to figure this one out? Is there a fuse that would leave the lights running, but unable to adjust? Would there be some wiring somewhere that I can inspect? I'm pretty comfortable opening things up, but I don't have a voltmeter or anything else in the way of electrical test equipment (I could consider getting something, but it's not high on my priority list at the moment).

    Thanks for any thoughts/suggestions on where to look!
     
    #1 Fivel, Oct 16, 2020
  2. ChapmanF

    ChapmanF Senior Member

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    Vehicle:
    2010 Prius
    Model:
    IV
    Things I would check:

    1. Turn the headlight switch one click. Not two clicks to turn on the headlights. At the first click, the marker lights and taillights around the exterior of the car should be on. Are they?

    2. Go into the "vehicle signal check" screen on the MFD. (A lot of threads around here show how to do that; maybe search for 12 volt battery check, just because that's often what people want the signal check screen for.)

    The signal check screen doesn't only show the 12 volt battery reading people usually want. It will also show TAIL [ON|OFF]. Does that change appropriately, when you turn the headlight switch to the first click and back?

    Note: there should be two ways of getting to the signal check screen: one that involves the headlight switch, and one that involves touching the screen six times in two places. I would opt for the touch-screen method, since there's already a question about the headlight switch.

    With those results, we can think about next things to check. The panel lights aren't ever going to dim if the taillight signal isn't getting there.
     
    #2 ChapmanF, Oct 16, 2020
  3. Fivel

    Fivel Junior Member

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    Location:
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    Vehicle:
    2007 Prius
    Model:
    Base
    Thanks — I just tried these steps and taillights are working, and the on/off is showing up appropriately in the signal check screen. (Interestingly, the PKB does not seem to register the parking brake, but from what I gather from this thread (Vehicle Signal Check Mode, Curious | PriusChat), that doesn't seem to be an issue).

    Thoughts on next things to try?
     
    #3 Fivel, Oct 16, 2020
  4. ChapmanF

    ChapmanF Senior Member

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    IV
    Maybe take your list of lights on and about the instrument panel that aren't lighting up, look over the wiring diagram and see where they have a common upstream, and where the dimmer control sits in all that.

    Bear in mind that, for a 2007, some panel illumination lights not lighting up could easily be because they are just burned out.
     
    #4 ChapmanF, Oct 16, 2020
  5. Fivel

    Fivel Junior Member

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    Location:
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    Vehicle:
    2007 Prius
    Model:
    Base
    Just closing this thread: turns out I had the same problem as detailed over on this thread: Dash Dimmer Switch Not Working | PriusChat

    In short, the cable was disconnected. Had the panels open for another reason, saw the cable was not connected. Plugged it in, everything is fine.
     
    #5 Fivel, Jan 15, 2022
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