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Not able to get high a/c fan output while driving.

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by JeremyAndACat, Jul 16, 2024.

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  1. JeremyAndACat

    JeremyAndACat New Member

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    When I start my 2011 Prius I can usually get the highest fan speed going while it's in park but once I start driving it will put out air closer to a low or medium speed and I can hear/feel it fluctuating up and down. If I put the car back into park I can eventually get it to put out high speed air but it takes a few minutes. I suspect it's a bad blower motor and/or resistor but the fluctuating up and down only while driving isn't a symptom I'm seeing others experiencing. Any idea what this could be?
     
    #1 JeremyAndACat, Jul 16, 2024
  2. JeremyAndACat

    JeremyAndACat New Member

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    I should add that after about 25 minutes of running, the A/C seems to work normally.
     
    #2 JeremyAndACat, Jul 16, 2024
  3. JeremyAndACat

    JeremyAndACat New Member

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    And sometimes if I set the fan to the lowest speed for about a minute, the issue will be resolved.
     
    #3 JeremyAndACat, Jul 16, 2024
  4. ChapmanF

    ChapmanF Senior Member

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    Is the "auto" light on, or off?

    Does the blower speed bar graph on the display go up and down with the actual blower speed, or is the bar graph staying at full?

    Prius hasn't ever used a blower resistor, though gen 1 and 2 used a separate electronic controller that mounted in the air duct the same way an old-school resistor would, and sometimes people call it that.

    Gen 3 moved that controller into the motor itself, so there isn't even the thing-people-called-a-resistor. At least that reduces the number of parts to think about.
     
    #4 ChapmanF, Jul 17, 2024
  5. JeremyAndACat

    JeremyAndACat New Member

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    The highest fan speed fluctuates whether it's in auto mode or not. The fan speed goes up and down incrementally with the bar graph but the speed still fluctuates up and down.

    That actually is good news about the resistor, thanks!
     
    #5 JeremyAndACat, Jul 17, 2024
  6. ChapmanF

    ChapmanF Senior Member

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    I can't quite tell what you mean here. When you notice the fan speed fluctuating up and down, is the bar graph changing with it, or is the bar graph holding steady?
     
    #6 ChapmanF, Jul 18, 2024
  7. rjparker

    rjparker Tu Humilde Sirviente

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    I suppose you could have something jamming the blower like leaves or nesting material. Check the cabin filter.

    Perhaps one of the blend door or air routing servos is failing or slipping.

    A long shot would be the system is limiting the power to the AC system based on engine overheating.

    Techstream or other scanners could verify some of the air handler and compressor functions.
     
    #7 rjparker, Jul 18, 2024
  8. JeremyAndACat

    JeremyAndACat New Member

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    I checked and cleaned the cabin filter but while it was removed I noticed the fan speed was still fluctuating up and down.

    I'll look into the blend door and air routing servos.

    I'm guessing it's not overheating since it takes around 20 minutes or so for the fans to finally kick up to a fast speed and then it's generally fine until the car is turned off for a couple of hours. Also I have an OBD scanner and I've never had any codes that suggest overheating.

    I thought maybe it was the auxiliary battery since it's fairly old and I've been having random intermittent electrical issues like windows going back down while I'm trying to put them up and the bluetooth disconnecting and then reconnecting about once a week. The battery looks like it's in good health though.
     
    #8 JeremyAndACat, Jul 24, 2024 at 5:30 PM
  9. JeremyAndACat

    JeremyAndACat New Member

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    One other thing that I remembered was once during the last winter here I turned on the heat and it wouldn't pump out hot air until I turned the HVAC system off and on a couple times, then is started pumping hot air immediately. At that point I hadn't had any fan speed issues and I thought it was just a weird electrical thing like the windows/bluetooth.
     
    #9 JeremyAndACat, Jul 24, 2024 at 6:14 PM
  10. bbrages

    bbrages Junior Member

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    Probably need a new blower motor
     
    #10 bbrages, Jul 25, 2024 at 8:53 AM
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