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AC runs in winter

Discussion in 'Gen 3 Prius Technical Discussion' started by brakeshoe87, Dec 8, 2014.

  1. brakeshoe87

    brakeshoe87 Junior Member

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    Ever since I got it my 2012 Prius climate control has worked strangely. In the summer when I run the AC it runs for a bit and stops I suppose when the temperature is reached. However the strange part is that it switches to outside air. I was always told it was more efficient to run the AC on recirculate so you weren't cooling the outside air. The heater is even more frustrating. Whether I run Auto or manual the process is similar. It it is 30 outside and I turn on the heat the AC light goes on and so does outside air. If I turn off the AC and put on inside air it stays that way for a minute or two before going back to the outside air. Also if I switch the blower to the dashboard setting that always changes to floor after a minute or two. When it is on floor mode I can feel warm air seeping out at floor level but no strong stream of air. I have owned a lot of cars and have never run into this situation. The dealer says it is normal but there is nothing in the manual that supports that position. Is this how other people's Prius work?
     
    #1 brakeshoe87, Dec 8, 2014
  2. bisco

    bisco cookie crumbler

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    they don't want you to suffocate from no fresh air.;)
     
    #2 bisco, Dec 8, 2014
  3. Easy Rider 2

    Easy Rider 2 Senior Member

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    Can't say for sure if that is exactly right or not but it happens because:
    There is an inside humidity sensor somewhere and if that is too high it uses the
    AC and outside air to de-humidify.
    You really don't want to defeat that because under some conditions, your windshield can fog over REAL quickly and then it takes some time to clear it again.
     
    #3 Easy Rider 2, Dec 8, 2014
  4. David Beale

    David Beale Senior Member

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    You need outside air to keep the humidity down in the car.

    You are over thinking the system. Let it do its' thing. Unless you enjoy fighting it.
     
    #4 David Beale, Dec 9, 2014
  5. GregP507

    GregP507 Senior Member

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    I agree, don't fight the engineers who made the car as good as they could make it.
     
    #5 GregP507, Dec 9, 2014
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    I thought (might be wrong) if you push the Auto button, then push some other button, for example Mode, Fan Speed or Recirc/Fresh: that would override just that portion of Auto.

    For example, if you pushed Auto, and then set a particular Fan Speed, all the other factors would be adjusted by the Auto's decision, but Fan Speed would hold constant, where you set it.

    The one joker in the deck is A/C. I know typically if you've set Auto and do not have A/C button depressed (light out on A/C button), then A/C will not run. But if you set mode to Heat/Defog, it'll often run A/C behind the scene.

    The light on A/C button will remain dark, but it WILL run A/C, as evidenced by other-than-zero reading of XGauge ACw ((A/C watts) on Scanguage.

    But not always, lol: lately I used Heat/Defog with temps close to 0C and got continuous zero readings for ACw. Then even as high as 7~8C, continuing zero.

    And then it would start indicating higher than zero (A/C running). Not sure what's driving the decision: maybe temperature and/or humidity sensors? Not sure if the latter exists.

    Bottom line, it seems apart from A/C, most other vent system behaviours are controllable, predictable. I hope...
     
    #6 Mendel Leisk, Dec 9, 2014
  7. qdllc

    qdllc Senior Member

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    You are correct that recirculating the cabin air is more effective in reaching and keeping the desired temp, but humidity control is another factor the engineers consider. IIRC, the Prius will remain on recirculation mode if you are in a high humidity area during the summer because fresh air only makes the A/C work harder, but I'd need someone from such a place to confirm if this is so.
     
    #7 qdllc, Dec 23, 2014
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