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Thread: 4.2 electric fan help

  1. #1
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    4.2 electric fan help

    I have a 05 trailblazer with the 4.2 and would like to switch to electric fan. I would like to beable to use my hp tuners to control the elctric fan like I did on my 05 silverado. The fan is done with pulse withs or something like that. I am not sure if I can hook into the harness at the core support were the elctric clutch hooked into.

    Please scroll down to post 7
    Last edited by badbowtie; 12-01-2012 at 07:47 PM.

  2. #2
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    Never done this, but,
    You could you not goto fan table, select the temp you want to fan to turn on and put 100% there and up,
    Then where the wire goes to fan, put that to power a fan relay.
    Do the same with AC pressure table?
    Just a thought

  3. #3
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    Unless I am completely missing something I don't see that a option like my 05 ls1 has. Here is a tune you can see what I am talking about.

  4. #4
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    System > Fans
    fan desired% vs Coolant temp

    Lets say you want fans to turn on at 199*
    from 199* and up put 100%

    Then you would use the Fan PWM wire, hook into a relay, to turn relay on.
    Then wire relay to the fan motor.

    I cant see why this wouldnt work but I have never done it.

  5. #5
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    But I am just not sure this will work like that since I think it is a pulse with thing the fan tab looks nothing like my 05 ls1 like the trailblazer does. I would like to conform that would work before I start I have to finish in a evening so my wife can drive to work next day.

  6. #6
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    PWM Pulse Width Modified

    So for example if it was set a 50%, then it would be on 50% of the Time and Off 50% of the time.

    But if you set at 100%, it would be ON 100% of the time, so it would be a constant current and not a signal.

  7. #7
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    I still have never fixed the clutch fan on my wifes trailblazer just turned the ses light off. But it is starting to affect mileage so I need to get this figured out I finally did find a wiring diagram for the plug that the clutch plugs into. I also would like to here if this will work from someone that has done it since this is her everyday vehicle I can't have down time. Since it is PWM like planethax said can I just set it too 100% were I want it to turn relay on.