1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Question about air conditioning suddenly going full throttle

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Matt Price, Jan 18, 2018.

Tags:
  1. Matt Price

    Matt Price New Member

    Joined:
    Jan 12, 2018
    2
    0
    0
    Location:
    San Francisco
    Vehicle:
    2011 Prius
    Model:
    Three
    I have a low mileage 2011 Prius, and we can't quite figure out this weird thing that happens with the air conditioning system. It's been happening since we bought the car, so it doesn't seem like something has recently "broken". It's rare, rare enough that I haven't been able to memorize the particular settings that might trigger it, but it goes something like this:

    We turn on the air (heat, or maybe cool, may or may not have the actual A/C on) to about 2-3 bars. After a few minutes, it shoots to full throttle, all the way up, which is loud and very annoying. I read the manual, and it says something rather vague about the dust/pollen filter (the button third from the right, along the lower edge of the air conditioning display), something about the system turning off automatically. But I'm not entirely sure the dust/pollen filter is even on when it does this...

    Why in heaven's name does the darn thing go full-on like that?
     
    #1 Matt Price, Jan 18, 2018
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    108,036
    49,113
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    two things. if you accidentally hit the pollen filter or auto buttons, the fan goes to top speed.
     
    #2 bisco, Jan 18, 2018
  3. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,907
    38,356
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    Is this happening when the car's fully warmed up, or during warm up? If the latter:

    • The car will tend to ignore your HVAC requests, especially higher heat settings, until the car is at least partially warmed up. And once it crosses some temp threshold, then it'll allow the HVAC system to react, and if you've got the heat set fairly high, the fan will suddenly speed up, very dramatically.
    (I don't know how I got that bullet, stuck with it)
     
    #3 Mendel Leisk, Jan 18, 2018
    fotomoto likes this.
  4. jack black

    jack black Active Member

    Joined:
    Jan 5, 2018
    225
    142
    0
    Location:
    USA
    Vehicle:
    2010 Prius
    Model:
    I
    this or you are hitting the front defrost. i always stay out of auto mode and never use the pollen setting to avoid this.
     
    #4 jack black, Jan 18, 2018
  5. AzWxGuy

    AzWxGuy Weather Guy

    Joined:
    May 22, 2011
    973
    494
    0
    Location:
    Tucson, AZ
    Vehicle:
    2021 Prius
    Model:
    Limited
    You might want to try an HVAC test to see if there are any codes. The keystrokes for this test are start from ACC mode (power on without brake), hold down AUTO and Recirculate/Fresh Air buttons, and press START again. Should see A/C LCD and all LED lights blink 4 times at 1 second interval followed by a code displayed where the preset temperature (digits on left side of LCD) are normally displayed. A 00 code means no problems. Then press OFF to escape. If you get anything other than 00, then a visit to the dealer might be in order.
     
    #5 AzWxGuy, Jan 19, 2018
  6. Grit

    Grit Senior Member

    Joined:
    Aug 22, 2017
    6,117
    4,041
    1
    Location:
    Wilkes Land
    Vehicle:
    2012 Prius
    Model:
    Four
    My 2012 (mid fresh according to Raytheeagle) does the same thing, but it gradually goes from one bar to full blast all bars within 10 seconds. It goes to full blast no matter whether if temp is set for heater or AC after pressing the 'Auto' button. It doesn't matter if 'front' and/or 'rear' are enabled, even if neither are selected, when I press 'Auto' the system goes full blast.

    To me, I actually like it because I need the back window and windshield to be defrost/defog ASAP to clear up. It takes about 15 seconds for front windshield to completely defog. You probably do this already to stop the sudden full blast; pressing the 'Auto' button and immediately press the down arrow to avoid face full of heat or cold air.
     
    #6 Grit, Jan 19, 2018
    Last edited: Jan 19, 2018
    Raytheeagle likes this.
(You must log in or sign up to post here.)