Hot weather and alarms

Discussion in 'Gen 4 Prius Main Forum' started by Ampletum, Aug 31, 2019.

  1. Ampletum

    Ampletum Junior Member

    Joined:
    Jun 4, 2018
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    Location:
    Greater Manchester UK
    Vehicle:
    2016 Prius
    Model:
    Excel
    Hi all, I thought I would share my recent experience with you. Last weekend in the UK was a bank holiday (not Scotland) and unusually the weather was amazing with temperatures 0ver 30c. On Sunday morning my neighbour informed me that my car alarm had gone off at about 11.30pm. I had not heard this, two glasses of Malbec can put me out like a light!. I checked over the car and found no evidence of anyone trying to break in so I thought no more of it. Sunday night at 11.30 the car alarm goes off again. This time I hear it and switch it off. Monday night the alarm goes off four times between 10.30pm and 2.30am. Next day I called into my local dealership and a helpful young man came and had a look at my car. The first thing he did was open the boot and then say 'There is your problem' He pointed to thr plastic shopping bags which we keep there for our frequent shopping trips. He said there is a sensor in the bot and the extreme heat of the day had caused them to swell. When it cooled down they had contracted and this had set the alarm off.He kept the car overnight with no bags in the boot and the alarm did not go off.Mind you it was not as hot on the Tuesday night. Now that the weather is back to normal the alarm has not activated again, so fingers crossed. has anyone else had any problems like this? Please let me know
    Thanks
    .
     
  2. The Professor

    The Professor Senior Member

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    Location:
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    Vehicle:
    2017 Prius
    Model:
    Excel
    Weirdly, I had the same problem over the same days. I'm not convinced about the sensor in the boot. The ultrasonic sensors are located in the roof just backwards of the front ceiling light (looks like two small black holes in a rectangular piece of grey plastic). I would also be surprised if the sensors can detect at the distances of the boot contents, or through the seats/boot cover.

    Spiders and flying insects trapped inside your car can and do set them off if they fly close to the sensors. Sure enough, there was a fly trapped in mine.

    If it's just a single trigger, it's often caused by the seatbelts retracting a final inch.

    Another cause is leaving the windows open. I have mine set to all open if I long-press the unlock button on the fob. I sometimes accidentally do this while they're in my pocket. The doors will automatically re-lock and alarm arms if nobody opens a door in 30 seconds, but that leaves the windows open. Gusts of wind will set the alarm off if the windows are open.
     
  3. alanclarkeau

    alanclarkeau Senior Member

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    Location:
    near Brisbane, Australia
    Vehicle:
    2016 Prius
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    Very odd - I've never had an alarm and it's been well over 30 here - had over 40 one day, but quite a few 37/38.
     
  4. StarmanUK

    StarmanUK Junior Member

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    Nov 25, 2017
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    Location:
    Essex, UK
    Vehicle:
    2017 Prius
    Model:
    Business Ed. Plus
    I had the same thing approx 2 months ago and I believe it to be a moth trapped in the car. I temporarily solved the nuisance alarm activation by disabling the ultrasonic sensors which is an option upon power down for a couple of days in the hope that whatever was trapped would find its way out or passaway.
     
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