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Temperature coming from vents fluctuating between hot/ambient

Discussion in 'Prime Technical Discussion' started by HypersonicPrime, Apr 10, 2023.

  1. HypersonicPrime

    Joined:
    Oct 1, 2017
    74
    59
    3
    Location:
    NC, USA
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    Periodically I notice that my 2017 Prius Prime begins rapidly cycling the temperature between hot/ambient and it gets fairly annoying. For example, on a recent drive the outdoor temperature was around 50F. I had the temperature and blower set to Auto. The A/C was off and the temperature setpoint was 74F. For maybe an hour, it seemed to properly maintain this temperature. However, after a while it seems to get into a rhythm of full-heat and no-heat. The cycle period is maybe 10 seconds (I haven't timed it, so this is a guess). When everything is quiet I can also hear an actuator moving in conjunction with the change in temperature. This has happened several times and it seems to require some amount of time before it starts doing this (doesn't seem to happen immediately). I have only noticed it in heating mode. Has anyone else had this issue?
     
  2. mc357

    mc357 Junior Member

    Joined:
    Jan 7, 2022
    17
    1
    0
    Location:
    ct
    Vehicle:
    2021 Prius Prime
    Model:
    XLE
    I have the same issue. It's annoying.
     
  3. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    7,035
    2,782
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    I have the same issue but with a C.
    When you get real close to the set point, it has trouble maintaining.
    Both on heat and cool.

    And so does my Ford Fusion.

    I strongly suspect that neither Toyota nor Ford cares the least little bit.
     
  4. SSAutomotive

    SSAutomotive Junior Member

    Joined:
    Dec 15, 2021
    18
    2
    0
    Location:
    Stewartstown, PA
    Vehicle:
    2011 Prius
    Model:
    Two
    Bit out of date but I'd suspect the thermobulb, or whatever temperature sensor is used to be a culprit, OR the control unit itself.
     
  5. SSAutomotive

    SSAutomotive Junior Member

    Joined:
    Dec 15, 2021
    18
    2
    0
    Location:
    Stewartstown, PA
    Vehicle:
    2011 Prius
    Model:
    Two
    Bit out of date but I'd suspect the thermobulb, or whatever temperature sensor is used to be a culprit, OR the control unit itself.