2018 Prime advanced trim wipers won't turn off

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by frederw1701, Feb 24, 2025.

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  1. frederw1701

    frederw1701 Junior Member

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    Vehicle:
    2018 Prius Prime
    Model:
    Plug-in Advanced
    Every position on the stalk including Off runs at the same speed as long as the car is turned on.

    This started all at once.

    My usual independent mechanic is not familiar enough with the car to feel confident and they referred me to a dealer. I have a choice between one that doesn't return phone calls and one that we have avoided for decades.

    Is there a straightforward troubleshooting sequence for a problem like this? Is the best starting place the stalk, or the automatic wiper sensor?

    Update: dealership called back. They suspect the motor. ??. I am old and my picture of the world is that when you turn something off you cut its power. In which case the motor wouldn't run. Am I just obsolete, and it always has power but gets its ideas about how fast to run from the CANbus or something?
     
    #1 frederw1701, Feb 24, 2025
  2. ChapmanF

    ChapmanF Senior Member

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    Wiper motor assemblies usually contain a little switch to break a circuit when the wipers are in their parked position. The motor continues to get power when you switch them off, so it can proceed to the parked position where that switch then breaks the circuit. If that switch doesn't open when it should, you could see continued wiping.

    I take it they do stop when you power the car off? That's when the power supply is actually cut.
     
    #2 ChapmanF, Feb 24, 2025
  3. frederw1701

    frederw1701 Junior Member

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    Plug-in Advanced
    Correct, they run only when the car is in Ready or Accessory. I would seriously freak out otherwise.

    Thanks for the info about the motor. Is there also a known failure mode where the car acts as though the squirters were on?
     
    #3 frederw1701, Feb 24, 2025
  4. bennettlyle

    bennettlyle New Member

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    Disconnect the negative battery terminal for 5 minutes (make sure the car’s off and doors/windows are locked first) to let the car’s computer reset. Some other owners have run into the same problem – after cutting power, the wiper control module just fixed itself.
     
    #4 bennettlyle, Feb 24, 2025
  5. ChapmanF

    ChapmanF Senior Member

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    Um, dun᠎no. Is your car acting as though the squirters were on?

    How does a car that's acting as though the squirters were on act?
     
    #5 ChapmanF, Feb 25, 2025
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