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Thread: Cooling fan won't shut off except in 4x4

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    Default Cooling fan won't shut off except in 4x4

    I have a 1078 that the engine fan won't shut off. Not even when flipping the fan switch. My buddy has driven the truck more than I have, he said the fan shuts off if the truck is put in 4x4, this is what has me stumped. Everything appears to be hooked up.

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    Quote Originally Posted by NewEra View Post
    I have a 1078 that the engine fan won't shut off. Not even when flipping the fan switch. My buddy has driven the truck more than I have, he said the fan shuts off if the truck is put in 4x4, this is what has me stumped. Everything appears to be hooked up.
    Do these have a fan solenoid. If so unplug it and see if the fan shuts off.


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    The fan solenoid is normally closed which keeps the fan on. Unplugging it should keep the fan on. Sounds like an electrical issue. Maybe a ground somewhere.

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    Quote Originally Posted by Suprman View Post
    The fan solenoid is normally closed which keeps the fan on. Unplugging it should keep the fan on. Sounds like an electrical issue. Maybe a ground somewhere.
    So they do have them. I ask because you can get different solenoids that are normally open or closed so if he unplugs it and the fan stops someone may have replaced it with the wrong one. Also can check for power at the solenoid to see if it has power or not.


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    Screen Shot 2019-01-18 at 3.26.55 PM.png
    So does that mean the Cooling fan is off all the time? Because FMTV have permanent 4x4 wheel drive. Last time I checked on mine anyway.
    -Check if the circuit breaker is tripped CB22 if not then
    -find the cooling fan solenoid behind the passenger kick panel.
    take off the connector and check for continuity . then check fo voltage on the plug. supply voltage from a source and see if the solenoid engages. if it works then
    -deplete air from tanks and remove air line from cooling fan solenoid. if air pressure builds , shut off the truck.
    -Remove Solenoid and replace.
    I will either find a way, or make one!
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    I hate people, who use big words just to make themselves look perspicacious.

    1988 M813
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    Quote Originally Posted by 319cssb View Post
    Screen Shot 2019-01-18 at 3.26.55 PM.png
    So does that mean the Cooling fan is off all the time? Because FMTV have permanent 4x4 wheel drive. Last time I checked on mine anyway.
    -Check if the circuit breaker is tripped CB22 if not then
    -find the cooling fan solenoid behind the passenger kick panel.
    take off the connector and check for continuity . then check fo voltage on the plug. supply voltage from a source and see if the solenoid engages. if it works then
    -deplete air from tanks and remove air line from cooling fan solenoid. if air pressure builds , shut off the truck.
    -Remove Solenoid and replace.
    Iím guessing he means when you press mode on the keypad to lock it in 50/50 mode.


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    NewEra (01-18-2019)

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    General 319cssb's Avatar
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    Are you the OP? How come you always inject your opinion in other people's posts? They can answer for themselves, you know.
    I will either find a way, or make one!
    --------------------------------------------------------------------------------------------------------
    I hate people, who use big words just to make themselves look perspicacious.

    1988 M813
    1987 M1028A2
    1084 M1009
    1997 M1078

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    Quote Originally Posted by 319cssb View Post
    Are you the OP? How come you always inject your opinion in other people's posts? They can answer for themselves, you know.
    Always, I havenít been on here in almost a year. Plus you can use your brain also instead of being condescending to the op since we all know the vehicle has all time 4x4.


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    NewEra (01-18-2019)

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    Quote Originally Posted by redman333 View Post
    Always, I haven’t been on here in almost a year. Plus you can use your brain also instead of being condescending to the op since we all know the vehicle has all time 4x4.


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    So why did you have to make your educational comment, if we all know that.
    Good bye and good luck. #ignorelist
    I will either find a way, or make one!
    --------------------------------------------------------------------------------------------------------
    I hate people, who use big words just to make themselves look perspicacious.

    1988 M813
    1987 M1028A2
    1084 M1009
    1997 M1078

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    Wow sorry to the op for that little temper tantrum. Donít ignore him he does have some good points. One thing to add to his in case itís not obvious. He mentions checking continuity, Iím assuming he means checking continuity on the solenoid itself not the harness. Since I guess heís ignoring me now he may not specify that.


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