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Radiator Fan Mod

Discussion in 'Gen 3 Prius Accessories and Modifications' started by AzusaPrius, Jul 12, 2023.

  1. AzusaPrius

    AzusaPrius Senior Member

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    Has anyone thought about puting a switch to turn the fans on at will.

    If so how did you do it?

    Looking to do this mod to keep better control of the coolant temp.
     
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  2. sam spade 2

    sam spade 2 Senior Member

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    And what exactly makes you think that YOU know what the temp should be, as
    opposed to the temp that the designed system keeps it at......or the range it stays at ???

    I propose that you don't know that at all.
    Most people think their cooling loop runs too hot.......when it doesn't at all.
    Having it too cool can result in inefficient combustion and sludge formation in the oil.
     
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  3. Grit

    Grit Senior Member

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    Cool idea. I just grill block when city driving monitor temp with an app as it doesn’t even get up to 180F during summer morning shopping. People here get outraged when I say I grill block during the summers.
     
  4. ChapmanF

    ChapmanF Senior Member

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  5. AzusaPrius

    AzusaPrius Senior Member

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    I watch my temps a lot and my ICE is always around 180-195F but in the 100+F temps I have seen it at 201F and prefer if it was lower.

    I would like to turn the fans on at 185F when I go North on the 15 freeway or other steep climbs on these hot days versus letting it turn on by itself at I believe 204F

    Doing this will help keep the temp balanced near the 185 mark on those drives.
     
  6. sam spade 2

    sam spade 2 Senior Member

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    And that will accomplish........
    exactly NOTHING useful.
     
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  7. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Using AC at same time? That’d be akin to riding the brake.

    This logic drives a lot of your gizmo acquisitions.
     
    #7 Mendel Leisk, Jul 14, 2023
    Last edited: Jul 14, 2023
  8. AzusaPrius

    AzusaPrius Senior Member

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    For you maybe but not for me.
     
  9. jzchen

    jzchen Newbie!

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    Not sure how the Germans do it but funny you mention my wife’s Panamera coolant temp gets up to exactly 201 F and I have never seen it fluctuate once reached!

    I think you may have better luck with finding a cooler thermostat.
     
  10. ChapmanF

    ChapmanF Senior Member

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  11. BiomedO1

    BiomedO1 Senior Member

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    You can just place a resistor in parallel or series of the thermostatic switch that closes the fan relay circuit. Your buddies at project lithium can do the calculations for the resistor need to bring the trip point down to 180. Keep in mind that turning on your AC will also trip the fans ON.

    That's how I controlled my fans, when I was poor and couldn't afford a thermo-switch.
     
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  12. ChapmanF

    ChapmanF Senior Member

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    Given that the "thermostatic switch" operating the fan relays is the ECM, based on the input from the coolant temperature sensor, you'd have to do that by adding the resistor to that sensor. It would do the trick, but it would also change what any scan tool tells you the temperature is, make the overheat light come on earlier, and so forth. If you were watching a scan tool, you wouldn't think you had accomplished anything, because you'd still be seeing the fan come on when the reading was 95 ℃. :)
     
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  13. BiomedO1

    BiomedO1 Senior Member

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    Yep, that too. My old Honda's had an independent thermo-switch screwed into the radiator; that controlled fan trigger. Wasn't sure how the Toyota was wired; but would accomplish the same goal. You're correct that the scan tool would be lying to you - but he seems to have a lot of mods on his car already. An IR temperature gun would get you the true reading.
     
  14. Grit

    Grit Senior Member

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    That was the exact comment you left when posted long ago about summer lower grill block haha

    And my answer was before I turn on the ac, I make sure to block the upper grill to 100% also and then blast the ac on power mode.
     
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