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Heat keeps getting redirected to floor vents with dash vents selected

Discussion in 'Gen 1 Prius Plug-in 2012-2015' started by ualdriver, Dec 16, 2013.

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  1. ualdriver

    ualdriver Member

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    I drove the wife's PiP a couple of times this week in the bitter cold. Once the engine heats the air enough, I take the climate control out of auto, put the fan speed as high as it will go, then direct all the hot air to the dash vents so it goes directly into the cabin.

    However, after about 60 seconds or so, the climate system overrides my selection and switches to the floor vents. Even if I switch it back to the dash vents, the system just does its own thing and goes back to the floor vents after a short time.

    What gives?
     
    #1 ualdriver, Dec 16, 2013
  2. usbseawolf2000

    usbseawolf2000 HSD PhD

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    The heat raises up, so it is best to output heat from the floor vent.

    I always use the auto setting so I have not experience what you reported.

    Are you in ECO mode?
     
    #2 usbseawolf2000, Dec 16, 2013
  3. giora

    giora Senior Member

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    I will add also:
    Floor vents heating will also give some warmth to the battery. One of its grill openings is very close to the floor.
     
    #3 giora, Dec 16, 2013
  4. bisco

    bisco cookie crumbler

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    i keep mine on manual and floor/defrost or floor/ dash or floor only or dash only and have never had it change. it does change from recirc to fresh quite often tho.
     
    #4 bisco, Dec 16, 2013
  5. ualdriver

    ualdriver Member

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    All through bisco.......

    Yes, I've read the argument that the floor vents are best because heat rises, but I find the cabin heats MUCH more quickly with the panel vents at max fan speed once the air gets warm enough, especially if you have people in the back. Once the cabin gets up to temperature, then I switch to the floor vents (i.e. I just let AUTO do its thing)

    Yes, I am in ECO mode.........and maybe that's my problem right there. Perhaps I should have taken it out of ECO mode as ECO might have been trying to override my decidedly non-economical behavior. I'll have to try that next time.

    Which leads me to my next question which probably now needs no answer.....why wasn't my Prius using the maximum fan speed to warm the cabin up once the air was hot? Probably because I was in ECO!
     
    #5 ualdriver, Dec 16, 2013
  6. jdk2

    jdk2 Active Member

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    Yep, ECO prevents the fan from running at MAX.
     
    #6 jdk2, Dec 16, 2013
  7. ualdriver

    ualdriver Member

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    Well, that fixes one of my problems :)
     
    #7 ualdriver, Dec 16, 2013
  8. bisco

    bisco cookie crumbler

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    i'm always in eco, so that's not the reason for the vent shifting.
     
    #8 bisco, Dec 16, 2013
  9. SLOW_RR

    SLOW_RR Member

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    ual... Are you by any chance using the front window defrost button (right above the Rear Window Defrost)? I ask because that will stay on only for a few minutes and then default to the regular cabin heating.... I have only had the "Auto" setting change on me if I shut the car off. Then it goes back to the default setting.
     
    #9 SLOW_RR, Dec 16, 2013
  10. ualdriver

    ualdriver Member

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    No, I don't think so. Just highest fan speed and selecting front vents with that button that has arrows pointing in two directions.
     
    #10 ualdriver, Dec 17, 2013
  11. Michael33

    Michael33 Member

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    The one with arrows pointing in two directions is the Hi/Lo position - both horizontal and floor vents at once. I was actually going to suggest that you use this one, instead of midlevel only. Since it only seemed to happen in very cold weather, I agree with the poster who thought it was trying to warm the battery pack by directing warm air towards a pack vent intake...
     
    #11 Michael33, Dec 17, 2013
  12. ualdriver

    ualdriver Member

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    Doesn't that button alternate air direction between the forward panel and the footwells? That is what mine seems to do. Regardless of the desire to warm the battery more quickly or having the air flow at one's feet because it might be considered better by some, one would think that if I manually direct the air to come out of the dash vents with that button, that it should stay that way until I change it. That's the part I'm not getting.
     
    #12 ualdriver, Dec 17, 2013
  13. bisco

    bisco cookie crumbler

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    agreed, i don't think anyone else has seen that happen. i drive as low as a few below zero and have never seen it. stays wherever i put it.
     
    #13 bisco, Dec 17, 2013
  14. ualdriver

    ualdriver Member

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    OK, thanks. I'll add it to the punch list when the car goes in for its first maintenance event.
     
    #14 ualdriver, Dec 17, 2013
  15. Michael33

    Michael33 Member

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    No, the airflow is supposed to be split between the two sets of vents, and stay that way. I think you have either a vacuum leak or an electrical problem that is messing with your vent actuation.
     
    #15 Michael33, Dec 18, 2013
  16. drash

    drash Senior Member

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    Hmmm, I don't drive in ECO at all. I'm not sure it helps in the winter although I can see where reduced pedal feel might help with roads covered with snow. I just put the seat heaters on high and leave the heat on Auto. If I need heat I just turn the temperature up and the fans adjust accordingly. My typical cabin temperature setting varies between 74 and 78. Been below zero a couple of days the last week or so.
     
    #16 drash, Dec 18, 2013
  17. Andyprius1

    Andyprius1 Senior Member

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    The only HV BATTERY protection I know of is during Summer with the driver turning AC on. The whole HVAC system is mind boggling, only slightly better than the Gen II. The Prius C is much better, but still not really accurate, and slow to react.
     
    #17 Andyprius1, Dec 19, 2013
  18. Michael33

    Michael33 Member

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    It's not just reduced feel. You also get better modulation of throttle position, because the whole pedal travel is still there, but translates to less throttle opening total. (The Leaf, BTW, still gives you full power if you floor it in Eco. This is better than the Prius algorithm.)

    ​
     
    #18 Michael33, Dec 19, 2013
  19. jdk2

    jdk2 Active Member

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    The Prius does too. Floor it in any mode and you get full power.
     
    #19 jdk2, Dec 19, 2013
  20. markabele

    markabele owner of PiP, then Leaf, then Model 3

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    Wow, I bet the ICE never shuts off at 78 inside and below zero outside. Hopefully you are grill blocking?
     
    #20 markabele, Dec 19, 2013
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