Understanding the A/C Buttons

Discussion in 'Gen III Prius Care, Maintenance & Troubleshooting' started by DanCole42, Mar 27, 2012.

  1. DanCole42

    DanCole42 New Member

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    I have a two questions on the A/C in my new 2012 Prius.

    1) Recirculated vs Outside Air. My question is, why would you ever set this to something other than recirculated??? Whether you're cooling or heating, it seems like it would be much more efficient to cool or heat air that's already been heated or cooled.

    2) The A/C button. What exactly does this do? I've grown up thinking that "air conditioning" is synonymous with "the thing that makes air colder." If I have the temperature set to a cooler temp, but turn the A/C off, what happens? If I have the temperature set to a hotter temp, but turn the A/C on, what happens?

    Thanks!
     
  2. jdcollins5

    jdcollins5 Senior Member

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    1) If you keep it on recirculate for too long the windows can start fogging up. Once the cabin temp setpoint is reached it is better to bring in outside air both for you and the HV battery, as the cabin air is used through the rear vent for the HV battery. If you leave the system in Auto it will choose the proper time to switch from recirculate to outside air.

    2) The A/C button is used mainly in the spring or fall mild weather where you may choose to just use fresh outside air versus AC. Even with the A/C button off, if you choose defrost the system will use the AC anyway to control humidity.

    So, if you have it set for cooler temps with the AC off you will get fresh outside air on the face vents. If you have it set for warmer temps with AC on you will get heat at your feet with no AC.

    I have found it best to leave the system in Auto and just set the temp setpoint to get the cabin temp and fan speed that I desire. The system is a really smart system. I usually leave the AC off unless I want the AC on.
     
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    Well, you've also got two threads regarding the AC, lol. Assume the moderators will delete the older one. Anyway:

    1) I would only rarely (if ever) use recirc with AC, just to speed up cooling. Or temporarily if it's really dusty outside. It's akin to breathing in a paperbag after a while.

    2) As far as I know, AC will not run, ie the compressor is off, without the AC button depressed. Exception being if you hit the front defog button. As far as the temp control, it will do what it can without AC if you set a cooler temp, but can't get the temp any lower than outside ambient temp, without AC button depressed. Raising the temp is never a problem, at least once the engine is warmed and there's hot engine coolant available.
     
  4. tach18k

    tach18k Member

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    I almost never drive with outside air on, my goodness, a car full of truck exhaust or from an older car. My windows do not fog unless it is very cold outside and I'm very hot, then the humity will sit on the windows, then a quick launch of the A/C and it clears up. The prius is different than most cars, my ford truck allowed me to set the incoming temp into the cab reagrdless if it was open air or recirc. I set mine at 70, pretty much leave it alone. If it gets hot, I use the A/c button.
     
  5. Myself248

    Myself248 Junior Member

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    So if I just want fresh outside air, with no temperature change effected by the car, I should set the temperature to "LO" and with the A/C button turned off, and this will neither heat nor cool the air on the way in?

    First car with the too-smart temperature control, forgive me if I wish it was still manual.

    Speaking of which, is there a way to lock the vent control so it *always* uses the face vents? It's simply infuriating that when I turn the thing off and back on, it "turns the knob" for me to pick a setting I don't want. Manual knobs knew when to stay put.
     
  6. Matt M.

    Matt M. Member

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    I believe most cars with auto climate control are similarly complicated... to get fresh outside air with no temperature change effected by the car in our 3 other cars we've had recently with auto climate control - 2000 BMW 3 series, 2005 Subaru Legacy, 2008 Honda Odyssey minivan - it's just as difficult/complicated. But some definitely work better than others. I was always unhappy with the auto climate control in the Subaru, but it works fine in the BMW and Odyssey and I've been happy with it in my Prius (purely in terms of how much fiddling I have to do to feel comfortable, temperature-wise).
     
  7. macman408

    macman408 Electron Guidance Counselor

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    Yes, LO with A/C off is good for just bringing in fresh air.

    If you want full manual control, don't press the Auto button. To turn it on, press the Fan ^ button to the desired level. The mode should remain at whatever it was previously; so if you set it to Face, then hit Fan Off, then hit Fan ^ to turn it on, it should still be on face. It should also be on face any time it is trying to cool you down (e.g. if it's set to LO).

    Personally, I generally just leave it in Auto with the A/C off, and set the temperature to get it to control the fan speed and vent selection to keep me comfortable.
     
  8. 9G-man

    9G-man Active Member

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    First stop thinking of A/C as just cooling.

    Start thinking Climate Control.

    A modern system like in the Prius is truely that.
    The fully automated heating, cooling, de-humidification, ventilation, circulation and re-circulation of the air in the cabin.

    Auto allows automatic climate control. All of the above is fully sensor and computer controlled for your comfort. All you do in AUTO mode is change the temp up or down for your comfort level. Everything else including fan speed is automatically controlled .

    A/C means the airconditioning compressor is engaged . Along with cooling it performs de-humidification. It alone (no AUTO) is Basically dumb airconditioning in any old car where you control everything else. Most of the time it is never understood or controlled properly anyway.
    Ref. some the comments above.

    Recirc is choosing to close off the cabin from outside air. Great for quick and efficient cooling of a hot, heat soaked cabin. (and AUTO mode uses it just for that)
    Also good for stopping outside odor and heavy smoke, smells from entering the cabin. (driving through that cloud of diesel, or dirt)
    The drawback is recirc cabin air becomes humid, smelly, stail, low on oxygen and high on carbon dioxide.
    You should not drive for long periods with only recirc air.

    Leave it in AUTO, and simply adjust the temp for your year around comfort, and enjoy modern climate control. And select recirc occassionally during your drive, when needed to keep out the nasty stuff.

    And Now we know why temp and recirc were placed at our fingertips, on the steering wheel.
     
  9. macman408

    macman408 Electron Guidance Counselor

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    Actually, it's not. If the cabin temperature is warmer than ambient, as it will be on a sunny day, you're better off using fresh air at first. Once the inside temperature is cooler than outside, you'll get a benefit from switching to recirculate; the cooler the interior temperature is (relative to ambient), the bigger the benefit.

    So recirc is a more efficient way to maintain the temperature inside the cabin, or to perform the last half of cooling the cabin when it's very hot - just not when the cabin air is still very hot itself.

    Personally, I just open the windows and turn on the vent for a few minutes to get the hottest air out. After that, I'll turn on the A/C.
     
  10. 9G-man

    9G-man Active Member

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    And your Prius proves it everytime the cabin is super hot and the auto a/c starts. It starts in Recirc mode until the cabin cools down. They designed it that way for a reason.
    And you are right......Rolling the windows down as you are moving to evacuate the sweltering interior heat helps greatly too.
     
  11. janice45

    janice45 Dudley Girl

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    Just a quick question
    any one have wet feet on drivers side while running air conditioning
    My floor is soaked
    Any ideas
    Thanks
     
  12. Tideland Prius

    Tideland Prius Moderator of the North
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    Nope and there shouldn't ever be any water inside the cabin!
     
  13. stanwirth

    stanwirth Junior Member

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    The drain line is probably plugged. Normally you will see a damp spot under the car, after using the air conditioner, when it is parked. Somehow the drain line from the condenser coil has gotten dirt or something else (mold) in it.
    You might want to see the dealer to find the line and unplug it.
     
  14. Mikawa

    Mikawa Junior Member

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    Outside-air option: this is your savior whenever somebody inside the car farts and you can't open the windows coz its raining or snowing like heck outside! o_O
     
  15. john1701a

    john1701a Prius Guru

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    Once upon a time, it was possible to for the line to get plugged by ice... the right set of circumstances having it freeze up from heavy use of the A/C itself.

    In that case, the problem will resolve itself when it melts.
     
  16. Jonny Zero

    Jonny Zero Giggidy

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    I have not run heat in my car yet. Say it is 45 out and I have a setpoint of 60 and hit the auto button, does the AC light come on with it? If it does, does the compressor actually run or only runs as needed to dehumidify the cabin?
     
  17. jabecker

    jabecker driver of Prii since 2005

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    There's a button for that. It looks like this:

    microfilter.JPG

    It recirculates the inside air through a micro-filter for 3 minutes. It's intended to rid the air of pollen and dust. But it also works quite well for the application you mentioned. :D
     
  18. Jonny Zero

    Jonny Zero Giggidy

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    Is the pollen filter laced with activated charcoal for smell removal?

    Personally my solution is the all four window auto down function. Nothing purges your cabin quicker than four open windows + 60 MPH.
     
  19. jabecker

    jabecker driver of Prii since 2005

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    Which probably works great in Austin, or in Portland in the summer. But in the winter... not so much unless you want to be very wet.
     
  20. Jonny Zero

    Jonny Zero Giggidy

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    Yes we are praying for rain. Again. Brush fires are starting again.