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Thread: Why is it a mystery on how to make E fans work

  1. #1
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    Why is it a mystery on how to make E fans work

    on 2012 Silverado 2500 with an E78 ecm.fo some reason I can not for the life of me get the fans to turn on. The first question will be are they wired up correctly? To the best of my ability.. on my VCM scanner i can trigger them on and off and in my tune if I add a "l" to output vs state always on when the key is on they turn on but not with ECT.
    That being said,dose the a.c. pressure sensor pay a roll in the e fan activation i.dont have that hooked up
    And 2..is there a special software that the ecm would have to be flashed with at the factory in order to run fans. This truck came stock with mechanical fan so I used the wiring schematics off a chevy cruze since they use the same ecm. Any help would be appreciate as the vehicle is running and driving "swap" now,I would like to keep it cool and not revert back to the mechanical fan.

  2. #2
    I’m not sure if this will work, but if the A/C pressure sensor connector is still there, I suggest that you would plug that onto a pressure sensor (even if you don’t have the A/C installed/connected on your vehicle) and then adjust all the settings in the A/C pressure/fan percentage table to 90% and see if the fans run then.
    2013 GS A6: Magnuson Heartbeat @ ~13psi; Kooks 2? Headers w/ ORX & NPP; Racetronix FPH w/ ECS Stage 1; GMPP CNCed heads; Vengeance cam (223*/239*,.610"/.623", 118+4*); BTR .650 springs; Melling HV/HP Pump; ID850 injectors, IW 10% OD Balancer, Dashlogic; PLX Gen 4 WB; MM catch can; 160* stat; FTI 3600 stall; NW Boosted 102mm TB

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  3. #3
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    Not a mystery, just a lot of parameter changes required to enable the cooling fans on an E78 HD truck. You mentioned looking at Cruze E78 schematics to help with wiring the fans. I would suggest doing the same thing (looking at a Cruze E78 tune) to setup the programming for fan control.

  4. #4
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    Good morning and thank you for your replies guys the fact that I checked the tune a million times and tried every way possible and still doesn't work boggles me. I have in fact copied the tune from a Chevy Cruze exactly to no available. If in fact the ecm requires the AC pressure switch to be hooked up to work would be a design flaw to my knowledge because if it requires it to be operable for the fans to come on if at any time the switch would go out, your truck would overheat so I'm no engineer but if I was an engineer I would make it default to work regardless if AC pressure was working or not.

    However I will hook up a pressure sensor on it and give it a try.i still think hptuners is missing some tables to make it work OR I'm missing somthing In another place of the tune where it be the engine tab or what have you.. keep the ideas coming I'll keep working on it and if you need more info to try and help me just ask I will reply and post whatever is needed and thanks for the help..

  5. #5
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    I have added the a.c. pressure transducer. Still dose not work..anymore suggestions?

  6. #6
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    Anyone else have any ideas?

  7. #7
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    set the a/c pressure criteria to allow the system to be enabled to 0 psi for A/C on & fans enable. set RPM max limits for clutch disengagement as well as appropriate max ECT temps when to auto-off. The areas will not be just in one area of hpt editor.
    I have a burrito in my colon, yet refried beans come out...
    How i know it's from the same meal? I didn't ingest corn any other time.

  8. #8
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    tune

    ive tried everything that the editor lets me do this is why i think some tables are missing. i will post my tune and you can check it for me. i am not running ac.

  9. #9
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    in your relay controls [ecm18040] change the 1-2 to 90 because u only have 2 fans, and then relay output 1 v state [ecm18047] put a 1 in the second box also, then in the control by % [ecm18060] change the 50 to 51 and the 90 to 91 then the 2-1 60 change to 50 and the 1-0 change to 25, see if that helps at all just worth a try, also not sure if u have to select a "radiator coolant sensor" for it to work also ?

  10. #10
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    Done.. ill load it tomorrow and check it

  11. #11
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    flashed it ran it and still nothing. i did however noticed my o2 sensor number 2 bank is slow acting i have headers on it ill have to look in to that later.

  12. #12
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    yea not sure then sounds odd if u can turn them on with the controls but not themselves come on, can u log all the fan info u can see what the desired % is doing ect and fan 1 2 if they say they are on or off, if u do a search on here i have a feeling there was a thread in the last few months about the fan controls but not sure what the outcome was

  13. #13
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    Does the ac comp clutch engage?
    I have a burrito in my colon, yet refried beans come out...
    How i know it's from the same meal? I didn't ingest corn any other time.

  14. #14
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    fan operation on e78

    Quote Originally Posted by * _ * View Post
    Does the ac comp clutch engage?
    i an not using the ac system however all wiring is there and hooked up. dosnt the bcm command the ac clutch on?
    i have exhausted Google search and found a few threads here and in other fourms with little to no response to them. i will try and log as much info on the ac and fans next time i start up and post it. i still think there is a few tables either on the fan tab or elsewhere on the tune that would enable or direct it to listen to ect or something or maybe the OS thats flashed into these trucks engines are with out the supporting software for electric fan operation until then keep the ideas coming and ill keep trying to get these to work. thanks guys for yalls help
    Last edited by 1211990984; 12-27-2017 at 09:26 PM.

  15. #15
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    not sure if it will help but worth a look
    https://www.hptuners.com/forum/showt...r-lack-thereof

  16. #16
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    fan thread

    Quote Originally Posted by 07GTS View Post
    not sure if it will help but worth a look
    https://www.hptuners.com/forum/showt...r-lack-thereof
    yeah seen it.. my fan never come on unless i change the 0 to I on all the out #1 vs state not even if i max out the tables to 100% but they tun on with the vcm controls

  17. #17
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    ok if changing that 0 fan relay to 1 brings them on it sounds like it is working but just the trigger to turn them on like the desired % or ECT setup or something like that isnt configured correctly, usually the "fan state desired v current state" and the "fan desired% v ECT" work as in the 0-1 is say 50 so having the 51 in the "desired% v ect" waits till the ect is at the temp the 51 is in and because its over 50 it brings on the fan, and then same logic for the 1-2 90 it waits till the ect that the 91 is in then it brings on the fan2 and then reverse to turn them off in the table.
    for a test in your [ecm18060] in the 89c first cell see what number u can put in there to bring on the fans with engine up to or over that temp, the relay 0-1 is 50 so a 51 should work but just make it higher and lower to see if any number brings on fan1, it will depend on what the ecu's fan desired % (log all the fan pids) is so if that isnt showing over 50% then it wont bring it on if its reading lower just lower your cell number to below it to see if it works
    also just noticed your a/c settings are both 0 and both 100% maby change those to different on and off numbers encase its freaking out
    Last edited by 07GTS; 12-28-2017 at 12:09 AM.

  18. #18
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    i got it i will try that tomorrow. what should i change the ac settings to?

  19. #19
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    tune

    i have attached tune

  20. #20
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    if ur not using the a/c then just something low in the rpm like 10 rpm disable and 5rpm re enable so above 10 its disabled and it will never go below 5 rpm running so it will stay disabled and same with tps maby 2% and 1%, it may not do anything but some other things can cause issues with a same turn on and off setting, also does adding the coolant temp sensor "enable" help anything just encase its not looking for any switch point with them all turned off
    Last edited by 07GTS; 12-28-2017 at 12:52 AM.