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HVAC Question................. Is AUTO the best setting?

Discussion in 'Gen 4 Prius Main Forum' started by atterbury90, Nov 27, 2019.

  1. Mendel Leisk

    Mendel Leisk Senior Member

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    Just checked, yeah it does, with a possible caveat. Anyway, what I did:

    1. Pushed AUTO.
    2. Overrode MODE, setting it to HEAT/DEFOG.
    3. Pushed OFF.
    4. Pushed Fan Speed Up button.

    The system "woke up", still in HEAT/DEFOG mode.

    Caveat: I was just doing this in accessory mode, with car stone cold. I don't think the fan speed was kicking in yet. I have done this in the past, and the one problem IIRC: when I push Fan Speed Up button, it does wake the system up, but I believe it also put the fan speed in manual (not just the MODE override).

    Ideally I'd like the system to be automatic, fan speed controlled by the car, and just the mode override.
     
  2. Chris Wolfgram

    Chris Wolfgram Active Member

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    Huh ? How about just hitting the AC button and turning the temp down as low as you want it ?

    I'm still trying to figure out what auto does that just setting a temp with AC either on or off, does not ?

    In other words, I would think "climate control" IS automatic, by default, no ?
     
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  3. bisco

    bisco cookie crumbler

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    You’ve lost me here Mendel. Aren’t we just talking about auto v manual?
     
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah maybe off topic. I'm trying to determine if you can:

    1. Set it to auto.
    2. Override just mode.
    3. Turn system right off.
    4.. Some how turn the system back on as it was.

    Don't think that's possible. Turn it back on by hitting fan speed up will restore the previous state (as it was in #2), but will also make the fan speed manual.
     
  5. bisco

    bisco cookie crumbler

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    Ya, can’t help you there. But I would really like to know why some gen 3 and 4 owners think auto is necessary and not just optional
     
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  6. Tideland Prius

    Tideland Prius Moderator of the North
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    Auto allows automatic control of the A/C compressor so it can come on and off as needed. (Versus manually turning it on and off with the A/C button).

    also, the automatic climate control has more fan speed steps which allows finer control of air flow and energy consumption. (E.g. the Gen 3 climate control had 21 fan speed steps versus the 7 steps in manual mode).

    ohh. No you can’t. Since you activate it by the fan speed or AUTO button, you do it the way you’re asking.
     
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  7. Mendel Leisk

    Mendel Leisk Senior Member

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    I have a scenario: the car is half-warmed, and I have everything on Auto, except mode set to Heat/Defog. I roll to a red light, and if I do nothing, the engine continues to run. But, if I turn the vent system right off, the car takes this as a signal that I don't need immediate warmth, and shuts down the engine.

    Now the light goes green, and I'd like to get going AND have the vent system exactly as it was prior. The only way I can manage this is to hit Auto and then Mode once (that one hit of Mode button at least always seems to do it, goes to the previous override).

    That's what I do, but it's goofy. Too bad they can't just make the Off button an Off/On button.
     
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  8. Tideland Prius

    Tideland Prius Moderator of the North
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    Yeah that’ll require an on/off button.
    I used to do what you do with the Gen 2. I used the AUTO A/C button on the steering wheel to turn the climate control on and off
     
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  9. alanclarkeau

    alanclarkeau Senior Member

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    If the car is heating (not a PRIME), it has to run the ICE.
     
  10. alanclarkeau

    alanclarkeau Senior Member

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    OK - I'm wrong (that make 2 times I can remember now o_O).

    It's 35°C outside - like HOT. POWER ON. Pressed "Fan OFF" - and that turned AUTO off.

    The fan stopped, the A/C light went off. Which is what I assumed was all it did.

    BUT

    When I flicked the fan speed up, the A/C light came on, and I could hear the A/C compressor start - and it started to cool down.

    So I assume it's an undocumented feature - and probably bypasses the temperature control, but it still read 26° - I didn't stay out long enough to see if it would create ice-cubes. Back inside in the A/C.
     
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  11. Mendel Leisk

    Mendel Leisk Senior Member

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    Sometimes, depending on the state of warm up, I can reliably turn the engine on/off by raising/lower the cabin temp setting. There's a threshold, around 20~21 C: tick it up, engine starts, back down, and it shuts off.

    It's currently -2c here, 9 o'clock in the evening. About the coldest it's been this fall.
     
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  12. sam spade 2

    sam spade 2 Senior Member

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    OR.....too bad that you can't just learn to live with the engine running that extra minute or so !! :rolleyes:
    :)
     
  13. bisco

    bisco cookie crumbler

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  14. kithmo

    kithmo Couch Potato

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    I use AUTO all the time cos I'm lazy and can't be doing with faffing about with different settings. Press auto button and away you go, I always leave the temp at 21.5 deg C, pressing the auto button again to turn it off.
    Nobody has mentioned the 3 AUTO settings you can cycle through on the Gen 4, ECO, NORMAL and FAST, am I the only one that uses them ?
    FAST setting warms the interior up quicker (the clue is in the name) but keeps the ICE on more.
    ECO setting dulls the heating a bit and uses the ICE less, turns off more at idle.
    NORMAL setting is a compromise of the above modes.
    The AC resumes whatever state it was in when you last used it, if you turned it off it stays off next time you press AUTO, if you turned it on it comes on the next time you turn on the climate with AUTO.
     
  15. Merkey

    Merkey Active Member

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    As the engine warms up, the auto mode ramps up the fan speed too high for my taste. I have to back the fan speed down manually and the auto mode shuts off.
     
  16. Chris Wolfgram

    Chris Wolfgram Active Member

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    I've never seen "Fast" or else Id certainly have used it on cold mornings when I first hop in the car....
     
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  17. kithmo

    kithmo Couch Potato

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    On mine you cycle through the 3 modes by pressing the AUTO button again.
     
  18. Mendel Leisk

    Mendel Leisk Senior Member

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    I try to leave the fan speed on Auto, and control the speed indirectly by adjusting the temp. For example, in winter, if the fan starts racing, I'll lower the target temp till it subsides. I do the opposite in summer with the AC.
     
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  19. bisco

    bisco cookie crumbler

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    but then it's not 'auto' :p
     
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  20. Mendel Leisk

    Mendel Leisk Senior Member

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    The temp setting is never on Auto. (n)
     
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