Traction battery fan — how to tell if it's working

Discussion in 'Gen 2 Prius Technical Discussion' started by Gwyneth, May 19, 2026 at 9:49 PM.

  1. Gwyneth

    Gwyneth Junior Member

    Joined:
    Jun 12, 2020
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    Vehicle:
    2004 Prius
    Model:
    Base
    This is regarding a 2004 Prius. After approximately 260k miles (I say "approximately," as the combo meter was working only intermittently for a couple of years until I replaced it), I finally cleaned my traction battery fan. Yes, it was as dirty as you think it was. Maybe even a little worse.

    Things seemed to go OK when I reinstalled the fan, so I hoped all was fine. But I can't hear the fan running, and according to Dr. Prius, the battery temperatures are 88-90°, which is coincidentally the air temperature in the car right now. I don't think the fan is running.

    There are only two electrical connections to the fan, and I plugged both in. I don't know what else could I could have done wrong.

    Does anyone know of a way of checking whether the fan really is working? I'd appreciate any and all suggestions.

    Thanks in advance.

    ETA: It's definitely not working. I'll check the fuses tomorrow, but I may just need a new fan. It is 22 years old, after all.
     
    #1 Gwyneth, May 19, 2026 at 9:49 PM
    Last edited: May 19, 2026 at 11:19 PM
  2. Georgina Rudkus

    Georgina Rudkus Senior Member

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    Vehicle:
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    Two
    I don't have a Gen 3. I have a Gen 3 2012 Prius v.

    I use a Scangauge 2 that constantly monitors the temperature of the HV battery.

    If the battery temperature does not rise above its design operational temperature, the fan is obviously working.
     
    #2 Georgina Rudkus, May 19, 2026 at 10:16 PM
  3. Tombukt2

    Tombukt2 Senior Member

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    All mine have been on original fans all of them HVAC HV battery etc just cleaned with a garden hose . And line dried till dry all impellers are bleached white no dust back in service headed to 665k he he .
     
    #3 Tombukt2, May 20, 2026 at 8:25 AM
  4. bisco

    bisco cookie crumbler

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    was there any corrosion on either side of the plugs? that's a common ailment. you can put a Kleenex on the intake vent if you don't want to obd
     
    #4 bisco, May 20, 2026 at 4:45 PM
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