engine fan runs constant

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Perchie15, Aug 4, 2023.

  1. Perchie15

    Perchie15 Light Load Member

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    I did by pass the coolant temp sensor that’s in the reservoir tank well the male side and fan still stayed on, WHERES the other sensor then?
     
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  3. JB7

    JB7 Heavy Load Member

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    The one in the tank should be the coolant level sensor. What year truck? Are there any codes? Did you carefully watch the video?
    Detroit DD13/15/16 I6 Engine Sensor Locations – TroubleCodes.net
     
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  4. Lazer

    Lazer Road Train Member

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    I believe that is true on the newer generation of trucks.
     
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  5. Perchie15

    Perchie15 Light Load Member

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  6. Perchie15

    Perchie15 Light Load Member

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    I did now and yeah it works!! No more constant fan!! Thankfully cuz lastnight we blew a belt on the truck. But still no ac compressor kicking in. Argh
     
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  7. gekko1323

    gekko1323 Road Train Member

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    So what was the problem? What exactly did you do to solve the problem?
     
  8. Perchie15

    Perchie15 Light Load Member

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    End up being a broken wire that crosssed under the transmission rubbed through.
     
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  9. gekko1323

    gekko1323 Road Train Member

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    Thanks for your quick reply. So what exactly did that wire have to do with the fan? My fan has been constantly on since I bought the truck, so I figured now was as good time as any to address it. It's not really doing any harm because the truck runs cool, even in the desert. But the 6.5 mpg and loss of power on hills has compelled me to finally fix it.
     
  10. Perchie15

    Perchie15 Light Load Member

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  11. Perchie15

    Perchie15 Light Load Member

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    It ran to the ac compressor and so that means the compressor wasn’t running at all and somehow that was signalling the fan to not shut off that that wire I believe ran to the ECM I never did follow it fully but was headed that direction.
    But there are a few reasons why the fan could be running constantly the hi/low pressure switches. And theirs a triangular switch also. But not all stars have that
     
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