Prius A/C operating details

Discussion in 'Gen II Prius Main Forum' started by fphinney, Sep 30, 2006.

  1. fphinney

    fphinney Member

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    How exactly does the Prius A/C system really work?

    For instance, if you ask for a low speed fan A/C system to perform, does it's power demand start to lessen as the car's interior approaches target temperature? Also, I am quite sure that the compressor shuts off, once target temperature is achieved - - Right?
     
  2. seasalsa

    seasalsa Active Member

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    <div class='quotetop'>QUOTE(fphinney @ Sep 29 2006, 11:15 PM) [snapback]325944[/snapback]</div>
    Maybe? Here is a great description of the Climate Control System by Tony Schaefer that I saved.

    Prius air conditioning system
    By TonyPSchaefer
    Let me tell you that I was impressed with the Prius air conditioning system right off the bat. Working for a building controls engineering company, I immediately related with what the Prius was thinking. There are some differences in the details between building controls and car A/C systems, but the basics are pretty much the same.

    Basically, it works like this: if the interior of the car is hot and you want it cold, the fan and compressors come on full-bore. On the other hand, if it's cool in the car and you want it slightly cooler, then they all come on slightly. As the temperature in the car reaches the desired setpoint, Prius recognises that it's getting closer and adjusts the compressor and fan accordingly. In that way, it eases into the proper temperature rather than running the fan all-out and then suddenly stopping (which is what most residential air conditioners do).

    In an over-simplistic way of thinking of it, think of the fan speed as the proportional difference between SETPOINT and CUR-TEMP. For example:
    SETPOINT=65º and CUR-TEMP=90º creates a high proportional difference resulting in a high fan speed.
    SETPOINT=65º and CUR-TEMP=70º creates a lower proportional difference resulting in lower fan speed.
    The Prius most likely recalculates several times per second (I'm guessing)

    Secondly, you might notice that the vents blowing the air change. Rather than blowing a bunch of air out of the dashboard vents and straight into your face, Prius will adjust so the air is coming out of the windshield vents and at your feet. As the airflow rate decreases, Prius will reroute the air to the vents. This is very smart since the sensation of comfort is a combination of temperature and air movement. Doing this, Prius can keep you comfortable simply by moving air, chilling it a little less and using less energy.

    Just like the variable transmission, you can think of the A/C as a variable system. Basically, if allowed to do it's thing without human interferance, it will work extremely efficiently.
     
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  3. fphinney

    fphinney Member

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    <div class='quotetop'>QUOTE(seasalsa @ Sep 30 2006, 08:00 AM) [snapback]325980[/snapback]</div>
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    SeaSalsa -

    WOW! Thanks, Great reply. I seem to have a little trouble getting satisfactory replies to questions & problems on this site. Other than that, this site is pleasantly unique.

    The Prius never ceases to amaze me. I keep on finding out more & more fascinating details about this engineering marvel!

    You made my day!
     
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  4. Tideland Prius

    Tideland Prius Moderator of the North
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    Not to mention that the Prius' A/C system is two-tiered.

    This means that during the winter (which is when this system shines), your windows won't fog up. How? When you start the car and ask for heat, the system goes into recirculation mode and you see the recirc symbol on the dash. However, while the air directed to the feet is recirculated, the air directed to the face is fresh air which means that the interior can heat up faster because of the recirculation but your windows won't fog (or defog faster) because fresh air is being directed at the face level.
     
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  5. ken1784

    ken1784 SuperMID designer

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  6. lisaann

    lisaann New Member

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    Hello,
    I have a Prius 2006 and I am getting ready to buy a new one.
    I have two Questions:
    2008 or wait for 2009? any opinions?
    Second question, has anyone had trouble with a mildew or mold smell from the AC vents when car is first started?
    Thanks,
    Lisa
     
  7. richard schumacher

    richard schumacher shortbus driver

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    It kinda depends on why you're waiting. I'd expect that the '09 is essentially identical to the '08, except that it will cost more. And if it does have major changes, do you really want to buy one of the first ones?

    Mildew can grow in the A/C in a damp climate. It helps a lot to periodically run the heater for a minute or two before shutting the car off, and to bring in outside air when the outside air is dry.
     
  8. la cucaracha

    la cucaracha New Member

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    You did see the "I'm guessing" comment right?
     
  9. picstart

    picstart New Member

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    The issue is forFlorida's highways the Prius 2007 A/C works for approx 90 mins then it cuts off . 30 mins later after driving with the windows down the AC will be back for another hour or more. This is by far the worst A/C we have ever had.
     
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I recommend that you have the car checked, to:

    1. make sure that the refrigerant level is correct.
    2. ensure the inverter coolant pump is operating.

    The behavior that you described is not normal and should not be accepted.
     
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  11. Ana Hernandez

    Ana Hernandez New Member

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    I am considering getting my AC system checked as well as it doesn't really reach the passenger back seats, I was surprised to find out the Prius has no back seat vents for AC.
    I had found one on the back arm side on the right but that's just the battery's vent for cooling. If I am wrong please correct me. Are all generations like this?
     
  12. bisco

    bisco cookie crumbler

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    yes, you are right. however, i have never had any complaints from the back seat. my a/c is ice cold, how is yours?
     
  13. Ana Hernandez

    Ana Hernandez New Member

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    My friends all deny the AC is low but I just know it is. But it is fairly ice cold when it feels like it, mainly when I am alone. Has anyone also noticed that MPG decreases as the AC is on?
     
  14. bisco

    bisco cookie crumbler

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    of course, it's a small hit, but it takes power from the battery which causes the engine to run more to recharge it. if you've never had your a/c maintained in 11 years, now would proly be a good time. and be sure to take it to a dealer, it's a unique system.
     
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  15. Ana Hernandez

    Ana Hernandez New Member

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    Yes, exactly I figured this same process before, because it's all connected to the battery and the engine. Sometimes I feel like I am forcing the engine by having the AC on automatic which stays on high the whole time. So then I turn it off before I can figure out if it'll ever lower itself. And yes I will be considering getting that checked unless I get some help from the DoItYourselfers. Thanks a lot I Aporeciate it!
     
  16. bisco

    bisco cookie crumbler

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    welcome. i run mine manually, one bar on the fan, temp set to low, push the a/c button on and off as needed. but if you want to use auto, just keep turning up the temp until you're comfortable, the fan speed should eventually decrease.
     
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  17. CrazyLee

    CrazyLee Member

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    I usually lower the windows for a few minutes while I start off. This can lower cabin temperature quite quickly. Then I run the A/C on high for a little with the dash vents on. It doesn't take long to settle down to what you desire for comfort.

    I have notice that I have a small noise from the front of the engine and I pinned it down to the A/C system. When I turn the A/C off that noise goes away. Since I never had the noise before I may be in need of service soon.

    Are there any experiences with this problem and prices of repair?

    Thanks in advance.
     
  18. Ana Hernandez

    Ana Hernandez New Member

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    I have the same happening to me, a noise on the front engine goes on when the AC system is operating. I will be taking it in for service, then I can inform you what pricing is like, at least down here.
     
  19. Data Daedalus

    Data Daedalus Active Member

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    To the best of my knowledge, the sound you are referring to is the A/C compressor / cooling fan noise. It is a bit noisy, and with the Prius being so quiet, you will definitely hear it with your windows down or when standing outside the car. This is normal.

    My 2008 Prius T Spirit has been doing this right from when I purchased it in June 2013. I always use the A/C during hot weather, and believe me, the minuscule mpg hit is always worth it. It's a nice trade off, as that very same cool cabin air is blown right through the Traction Battery and doubtlessly prolongs it's life, by reducing it's operational temperature during very hot days. It's used on damp foggy windscreen days during winter too! Always.

    Personally, I'd say the battery seems to hold a charge longer, and seems more willing to move the Prius in EV mode on a hot day, with minimal A/C "life support". I set my A/C manually, first expelling all hot air in the cabin at the beginning of my journey home.
    Then I turn the A/C on with fan at minimum setting and temp between 16c and 17c. Sometimes I'll use the second fan setting, but no higher.

    In this manual mode, the loss of mpg is truly minimal, and believe me when I say your Traction Battery will absolutely love you for keeping it cool during vehicle operation.

    Two years so far, and I've had no problems with my A/C system, though I'm also tempted to take it into Toyota for a checkup - just to make sure it's all running within design parameters.

    Sent from my GT-N5100 using Tapatalk
     
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  20. Ana Hernandez

    Ana Hernandez New Member

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    Thank you very much for your response!
    I now see it is a very common thing, I'll try to follow up with all the tricks and advice you guys have given me and I'll see how it goes.
    I honest never really used the fan unless is during winter for the heating system, but I will definitely give that a try! Thank you so much!