no power to fan solenoid

Discussion in 'Trucks [ Eighteen Wheelers ]' started by bowhunter67, Jun 24, 2017.

  1. bowhunter67

    bowhunter67 Light Load Member

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    Just had my cummins isx inframed with a new head and brought it home notice the fan would not disengage.unhooked air line to fan clutch it moved in and out checked for power to solenoid and no power with key on could not find any broken wires now stumped anyone with any ideas.
     
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  3. Alaska76

    Alaska76 Road Train Member

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    Did you check ALL fuses?
     
  4. bowhunter67

    bowhunter67 Light Load Member

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    cannot find any fuses for fan clutch unless it is labeled something else .
     
  5. lilillill

    lilillill Sarcasm... it's not just for breakfast

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    Most fan solenoids are controlled by ECM ground. They are inline with the ECM that turns on a transistor to complete the circuit to ground. Because they are designed as failsafe, the ground circuit is completed when the fan is not needed. Meaning, the solenoid is grounded, allowing air flow to the clutch to keep the fan off.

    If the fan solenoid fails or there is low air pressure, the fan will stay on.

    Because the ECM controls it, there are various things that will make the fan stay on...

    1. High coolant temperature.
    2. High AC pressure.
    3. Low air pressure.
    4. Either one of the wires are open.
    5. The hot wire is shorted to ground.
    6. The solenoid is bad.
    7. Blown fuse or bad relay.
    8. Bad ECM.

    Because you say there's no power at the solenoid, is there a blown fuse? Did a wire get pinched between the head and the block when they put it back together?

    Do not attempt to jump power to the solenoid wires unless you know for dang sure which one is hot and which one goes to the ECM. You'll smoke the fan MOSFET in the ECM if it gets 12 volts.
     
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  6. lilillill

    lilillill Sarcasm... it's not just for breakfast

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    Just go through the fuse box with a test light and check every one with the key on.
     
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  7. bowhunter67

    bowhunter67 Light Load Member

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    did that already all light up might try to jump the a/c sensor next with truck running then the temp sensor too.
     
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  8. Alaska76

    Alaska76 Road Train Member

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    That is precisely why I stated ALL fuses, there are times when a fuse is labeled as one thing but serves other circuits as well.
     
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  9. lilillill

    lilillill Sarcasm... it's not just for breakfast

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    I wouldn't do that. All of that stuff is connected to the ECM and it's way too easy to accidentally destroy a $3000 box if you send power down the wrong wire. Have a computer hooked up to it and see what the state of the switches and coolant temp the ECM is seeing.

    If the ECM says the fan should be off and the AC pressure switch and coolant temp agree, then you need to very carefully follow the fan solenoid wires back to the firewall, looking for any damage to the harness.

    Is this in the truck pictured in your avatar? Maybe someone with KW knowledge might know exactly which fuse/relay is for the fan solenoid.
     
  10. bowhunter67

    bowhunter67 Light Load Member

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    ok I'm going to take it back to the shop that did all the work to it tomorrow they have cummins insight let him deal with it because it worked before they overhauled it so they can figure it out and yes the truck in my avatar is the same one.
     
  11. bowhunter67

    bowhunter67 Light Load Member

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    found the problem the motor calls to cut fan off at 5 min after start the problem was the air line from solenoid to fan clutch it had a braided inner liner that had partially collapsed restricting the air flow.I could push shop air to the fan but there wasn't enough pressure from truck replaced line all good now thanks.
     
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