Bugs? (A/C and auto-high beams)

Discussion in 'Gen 5 Prius Main Forum' started by RogerPriusTX, Mar 4, 2025.

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  1. RogerPriusTX

    RogerPriusTX Junior Member

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    Yes, with the indicators set as they were the moment Auto was disabled.



    When it gets hot enough to use the A/C, I use Auto mode all of the time. In the spring & fall, I just want to vent outside air in... I assume I'll get better mileage than running the A/C (as I assume Auto would do). It's just a bit annoying that the car refuses to remember the last settings.
     
  2. RogerPriusTX

    RogerPriusTX Junior Member

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    Interesting... I leave the car's drive mode in "Eco" all of the time (on the theory that I get the best mileage there). I know that the A/C is always in "Eco" mode when the drive mode is "Eco". If I'm just using the vent, I don't think that this does anything, so I turn it off.

    I believe my A/C light went off when I pressed "Auto".

    I'm more annoyed now that the car is not remembering the last used mode.
     
  3. Prodigyplace

    Prodigyplace 2025 Camry XLE FWD

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    I think, among other things Eco runs the fan at a lower speed when in Auto mode. At least that was how the indicators appeared on my gen 4 Prius.On my 2025 Camry (Gen 5) the indicators do not show fan speed when in Auto. On my Camry the AC light is also off in Auto.
     
  4. KMO

    KMO Senior Member

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    Yuck, no thanks. I want to be able to request, for example, fresh air only while letting it keep control of everything else. Sure, losing partial auto loses the light ambiguity, but it's a significant reduction in functionality.

    Maybe I'm just used to this because it's worked the same way since Gen 2. Indicator behaviour has changed (so it's ambiguous in a different way), but the partial auto behaviour has been in use for over 20 years now.
     
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  5. Prodigyplace

    Prodigyplace 2025 Camry XLE FWD

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    Indicator behavior has changed since Gen 4, at least in my former 2017 Prius.
     
  6. RogerPriusTX

    RogerPriusTX Junior Member

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    Interesting that you say this... my 2018 Prius Prime did not work this way. I've only noticed it in the Gen 5.
     
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  7. KMO

    KMO Senior Member

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    The way the indicators displays what it's doing is different in the Gen 5, but the basic "partial auto" behaviour is the same in G2 and G5.

    I checked the G4 manual to make sure that it wasn't an odd one out, but it confirms it's the same:

    Presumably because the indicators always showed current state, you were misled into thinking that the G4 operates the way you say you want, and changed to full manual.

    The G2 to G4 had the problem you were complaining about the G5

    But with the G4 you didn't know that you didn't know... You only noticed with the indicator change in G5, which actually made that less ambiguous:

    G2 to G4:
    Full auto: Auto light on, other indicators showing state
    Semi auto: Auto light off, other indicators showing state
    Full manual: Auto light off, other indicators showing state

    G5:
    Full auto: Auto light on, other indicators blank
    Semi auto: Auto light off, some other indicators blank, some other indicators showing something
    Full manual: Auto light off, all other indicators showing something.

    Only remaining ambiguity is on the A/C light, I think, where "light off" can mean "off" or "blank" for auto. The other settings won't be blank when manual.

    It seems like you are having some problem with the car remembering the settings, but I'm going to put that down to the vagaries of the "My Settings" thing. You're not using different keys are you?
     
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  8. RogerPriusTX

    RogerPriusTX Junior Member

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    No, single set of keys. When I leave, I am in full manual mode: fan on at some speed, air source is outside air, and the A/C light is off. EVERY time I start the car, the fan speed is as I left it, but the air source indicators are blank, and the A/C light is off.

    Based on discussions with you, I don't know if the A/C is really running or not, so I have to hit the switch twice to ensure it is really off. I also select the air source I want.
     
  9. RogerPriusTX

    RogerPriusTX Junior Member

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    AHB report... Sunday evening, I drove the car and played with the AHB settings. It works as stated here; when I pull back on the stick and let go, the bright lights go off and stay off for a short time; I counted 8 seconds, but there was also a car coming, so the AHB may have kept the lights dim for an extra few seconds.

    I thank the forum and I'm glad to know this trick.
     
  10. RogerPriusTX

    RogerPriusTX Junior Member

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    You may be right, and I may play with the G4 car to verify this. My habit has always been to change the fan speed to (as I thought) turn off Auto mode. I don't think Auto mode would ever turn off the A/C. It could change the air source, but I never saw it.

    Instead, I think I can test this in the G4 by changing the air source; the auto light will go off, but, if you are correct, the fan speed should still be varied by the system.


    For what it's worth, I still think is it better that when full auto mode is disabled, the current air source and A/C settings should be shown.
     
  11. Hammersmith

    Hammersmith Senior Member

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    At the very least, why don't you go into the settings as has been described to you before and permanently take manual control of the A/C? That way you only have to worry about the air source(vent/recirc).
     
  12. RogerPriusTX

    RogerPriusTX Junior Member

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    Thanks, I found your post and I'll look at the Settings. I thought you had said it was under Vehicle->Climate, but there is no such setting there - just switches for Eco and Auto.
     
    #52 RogerPriusTX, Mar 12, 2025 at 11:07 PM
    Last edited: Mar 12, 2025 at 11:19 PM
  13. RogerPriusTX

    RogerPriusTX Junior Member

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    I played with the G4 settings tonight (a 2018 Prius Prime).

    The "Auto" control is one-way; I can turn it on, but it cannot be turned off by pressing Auto again [I expected this]

    Turning on Auto also turns on A/C [I knew and expected this].

    Turning on Auto sets the air source; usually to external - it recirculates when a large drop in temperature is needed [expected]

    Changing the air source or the A/C had no effect on the Auto light; it stayed on. I suppose one could consider this some kind of semi-automatic mode, since the fan is still controlled automatically, but at least I know whether the A/C is running and I know what the air source is.

    The ONLY way to turn Auto off is to change the fan speed. [not what I expected from the conversation]. As far as I can tell, changing the fan speed puts the system back into fully manual mode, with the A/C and air source left as they were when the fan speed was changed.
     
  14. Hammersmith

    Hammersmith Senior Member

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    The big infotainment screen

    Settings(gear icon)
    Vehicle Customize
    Climate
    A/C Auto -> change to OFF
     
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  15. KMO

    KMO Senior Member

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    Afaik, the A/C hasn't really been an "on/off" manual control since at least G2. It's not like it always runs the compressor when the light's on.

    It's always got an automatic component when "on", based on the current temperature and humidity and the target temperature.

    Disengaging "AUTO" disengages all the other controls from being manual, but not really the A/C.

    For the A/C the choices are basically "you can use the compressor to cool or humidify" (light on) or "you can't" (light off), even in manual mode. It's an enable for an automatic function, so only "off" is really manual.

    (The PHEVs add the wrinkle that it may run the compressor even with the A/C control off - to produce heat, or to cool the battery in the G5. The disable of the A/C button only extends as far as cabin cooling and dehumidifying - the traditional user meaning.)

    So the AUTO mode would never change that to the "you can't" setting - it would always use the "you can". But that doesn't mean the compressor's actually running even if the weather's cold. (And even if it is, it's variable speed anyway...) It's two automatic functions working in parallel - automatic air flow and automatic temperature regulation. The AUTO light is about the former, the latter is always active (unless you push temperature to LO or HI).

    Which then does rather pose the question - what's the point of turning the A/C light off in AUTO mode? Given that the A/C light is and has never been a status indicator, but rather a "permitted" indicator.

    I do recall the A/C enable toggle not affecting the AUTO light in G2 (it was effectively an independent control then - later there was a "turn it on when AUTO selected" option, but still semi-independent).

    As an extra complication - the interior/exterior control also isn't binary when in automatic mode - when it chooses to recirculate, it's often a "semi-recirculate" intermediate position, which doesn't have a specific indication.

    That contradicts the manual I quoted above. Are you actually testing this, or assuming the meaning of the AUTO indicator? You should ramp the temperature control up and down to confirm whether it's still changing other settings.

    Maybe the older cars were a bit more inconsistent in their handling of the AUTO light - it maybe didn't go off the moment you changed anything, like the G5. It's definitely true that the partial auto behaviour's always been there since G2, and I'm clear on the difference in the behaviour of the other indicators, but my memory is fuzzy on the detail of the AUTO light behaviour when partial auto is going on - I've been tending to take the old manuals' word for it.
     
    #55 KMO, Mar 13, 2025 at 2:43 AM
    Last edited: Mar 13, 2025 at 3:04 AM
  16. KMO

    KMO Senior Member

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    Actually, no the G5 is a bit squishy too - as described above for the G4 you can change the air inlet source to manual without the AUTO light going off. But not the fan speed or outlet direction.

    But that's not indicating any difference in behaviour, as far as I can tell - like the manual says, everything you don't touch remains automatic, regardless of the AUTO light.

    The AUTO light is just programmed to indicate "automatic fan speed or automatic outlet direction", and isn't affected by automatic/manual inlet direction, despite the button controlling it.

    How did the G4 display the inlet direction? G5 has separate lights for exterior and recirculate, so one of them is on if manual, and both are off if automatic.
     
  17. vvillovv

    vvillovv Senior Member

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    I was thinking about the changes in the HVAC system in Gen 4 after switching to Power Mode (Eco, Normal, Power) drive modes. I knew it would throw a monkey wrench into the convers above so I held off of that complication ....

    Another bit of possibly annoying info is that I think the HVAC indicators are different in Gen 4s with the 7" MFD screens compared to the 11" MFDs screens where the controls are mostly touch pad buttons.

    And I can only add what the 7" MFD screen model shows, so unless anyone is interested in how that looks, I'll just keep it to myself for now rather than add more confusion to the convers. :unsure:
     
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  18. RogerPriusTX

    RogerPriusTX Junior Member

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    Thanks; found it... but what does it do? It looks like it toggles whether or not pressing "Auto" enables A/C or not.
     
  19. RogerPriusTX

    RogerPriusTX Junior Member

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    I completely forgot to test the outlet direction.


    Still seems like Auto is only for outlet direction and fan speed; if I don't touch the intake selection, I don't think it would change... but this is harder to test.


    In my G4, there is a recycle button with a light -- when it's on, the air is recirculating; when it's off, it isn't.
     
  20. RogerPriusTX

    RogerPriusTX Junior Member

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    I had the G5 today (2024 Prius) and played with the settings.

    Just like the G4, changing the air source (outside air or recirculate) left the Auto light on, as did toggling the A/C button. I only got Auto to turn off when changed the fan speed. I hadn't read the post about the air destination; I assume that would have also turned off Auto.

    As expected, the Auto mode worked just fine.