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Cooling Fans: Any way to manually turn on/override

Discussion in 'Engine & Drivetrain' started by Foggy, May 26, 2020.

  1. Foggy

    Foggy Full Access Member

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    Well, I finally got all my stuff done on my 14 to tow over the holiday weekend.
    My bad news is that my fans don't come (are not commaned ON) at over 40 MPH

    This is bad news when towing heavy camper at highway speeds.
    As soon as I slow down under 40 mph, the fans are commanded on - 42%-92% and will
    cool things off.
    My fans are "tuned" to come on at 202* low speed and 212* high speed operation.
    But the "speed" is over riding that command I suppose. So my temps where constantly
    in the 214* to 230* Range and Tranny Temps along with it.

    I do have a "remote" switch for my C5 corvette that I can command to ON at any time, but the
    companies that make these are really just doing vettes/camaros/ mustangs.

    My cooling system is overbuilt with a Mishimoto radiator, B&M Trans pan (ext capacity&cooling)
    and I do have the "tow package" too.

    So... any help or ideas??
     
  2. Doubeleive

    Doubeleive Supporting Member

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    maybe have whoever did the tune try and fix that issue if that can't be done then my next best option would be to build my own relay and switch and patch it into the fan harness to "overide", I would wire the trigger to a key-on power only so I couldn't accidentally leave the fans running and kill the battery. I am pretty sure patching it into the existing harness wouldn't hurt anything since it just feeds off of another relay anyway. I would use good thick wire and a heavy duty relay those fans suck down some juice. I know you can get replacement male fan connectors so finding a female adapter would be nice so you could just make a plug-n-play harness and not have to cut the factory harness.
     
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  3. mikeyss

    mikeyss Full Access Member

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    That's odd that your fans aren't running when you go over 40mph, I know mine are on at those speeds. I've even heard my fans running on high speed going 50mph, however they didn't stay on high speed for too long at 50mph.
     
  4. Foggy

    Foggy Full Access Member

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    Yeah, my tuner I think screwed this one up... I thought the ECT always trumped
    the road speed as far as fans being commanded ON
    I'm disappointed with my tuner.. he's has had 2 set appts at 2+ days each
    to get this thing dialed in after my Edelbrock SC install...
    My trans shifting still isn't what I want and my MPG is horrible, still
    5 MPH towing and only 13 mpg all highway speeds..... I'm gonna have to
    go to plan B I guess.. But wanted to crutch my temps til I can figure
    this out
    Big Ass Radiator, 180 T Stat, Fans set to come on at 202*... I should
    be running cool as a cucumber !!!
     
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  5. thompsoj22

    thompsoj22 Full Access Member

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  6. swathdiver

    swathdiver Full Access Member

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    See post #337 at this link:
    https://www.tahoeyukonforum.com/threads/useless-information.97483/page-34

    You can turn the fans on with a Tech-2 or equivalent. Tuner should be able to address this.
     
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  7. Foggy

    Foggy Full Access Member

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    My tuner finally Emailed me back on this issue.. His response was: The fans
    are NOT commanded ON at Speed because turning them ON would create
    turbulance....
    So, I'm gonna find a new tuner of course because I'm still getting "surge" and
    that really sucks with Cruise Control ON -- and my MPG still sucks

    On a positive note: I talked to Mishimoto and described my highway speed while
    towing temp concerns. We spoke about the intercooler, trans, etc... And what
    it does w/o towing(normal temps), and what it used to do stock...
    He "thinks" maybe I have a partially blocked core internally in the radiator.
    I just need to uninstall it enough to get the serial # and my receipt and
    they will send me a new one!!! BTW, He thought the ram air at highway speeds
    with my set up should not need fans ON at speed. (and his name was "Jesus", so
    I'm gonna go with that for now.

    I have shoulder surgery next week, so I won't be able to swap out radiator
    for couple of months. So I won't have any info to follow up right away.

    I had to drive about 260 miles round trip hwy today with AC on and 83* ish
    ambient temps. My coolant never reached over 194* and trans never got
    over 175*.. Of course this was without towing anythibg
     
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  8. thompsoj22

    thompsoj22 Full Access Member

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    This change made a significant difference, The "holy grill" may identify DENALI as top of the line but it absolutely disrupts air flow. i dont know crap about wind tunnel testing and i have to believe that design engineers would not install a restrictive grill just for cosmetic's? im sure cooling fans flow identically behind the denali grill but without the fans on the sierra grill is far better, imo. Also in regard to foggy's post above, You have proven that your system is intact and functioning as designed under normal use. Forced induction is not normal and towing just add's to the burden, imo, You have to increase airflow

    View attachment 249045 012.jpg
     
    Last edited: May 31, 2020

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