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Fan won’t shut off on a C15 cat

Discussion in 'Peterbilt Forum' started by Perchie15, Jan 7, 2022.

Page 3 of 4
  1. Jan 10, 2022 #21
    Perchie15

    Perchie15 Light Load Member

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    Aug 16, 2021
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    Yup I’ve done that for longer that is to
     
    Perchie15, Jan 10, 2022
    Perchie15, Jan 10, 2022
    #21
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  3. Jan 10, 2022 #22
    Perchie15

    Perchie15 Light Load Member

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    Aug 16, 2021
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    I had unplugged that sensor and was still nothing and thrown me a engine code. When I did not 100% sure it was the intake sensor tho cuz that’s not the code that popped up
     
    Perchie15, Jan 10, 2022
    Perchie15, Jan 10, 2022
    #22
  4. Jan 10, 2022 #23
    Perchie15

    Perchie15 Light Load Member

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    Aug 16, 2021
    0
    I did wait for atleast over 3mins when I jumped the high pressure ac switch which is right above the rad right? I notice there was some switches in the ac lines along fire wall not sure what they were tho. Gather one was the low side? And no the computer just kept saying fan was on if that’s what u mean? When I pushed the fan override then it’ll pop on computer it was on or off
     
    Perchie15, Jan 10, 2022
    Perchie15, Jan 10, 2022
    #23
  5. Jan 10, 2022 #24
    Goodysnap

    Goodysnap Road Train Member

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    Jul 12, 2017
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    You need to monitor the AC fan request in the ECM-Something is commanding the fan to stay on. I think you are seeing the Fan on state, which will be on when the fan is. The Fan cycle switch goes open at high pressure to turn the fan on. So an open circuit will result in a fan on condition. Pull test the wires for being broken inside the insulation. Ohm the wires from the switch to the ECM. You are checking the correct one on the Rad. Should be a orange switch?
     
    Goodysnap, Jan 10, 2022
    Goodysnap, Jan 10, 2022
    #24
  7. Jan 10, 2022 #25
    Perchie15

    Perchie15 Light Load Member

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    Aug 16, 2021
    0
    Yea it’s orange. Jumped the prongs together n left it idle for awhile n nothing happened. Then the intake temp sender is on drive side above air compressor roughly? That’s what google showed me. I did find rubbed my though loom but wasn’t it. I’ll have to tackle it tomorrow n see. Any other switches that could be setting it to stay on?
     
    Perchie15, Jan 10, 2022
    Perchie15, Jan 10, 2022
    #25
  8. Jan 10, 2022 #26
    Goodysnap

    Goodysnap Road Train Member

    3,694
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    Jul 12, 2017
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    AC fan cycle switch and Cab manual On/off switch are most common. Cant think of any others at the moment
     
    Goodysnap, Jan 10, 2022
    Goodysnap, Jan 10, 2022
    #26
  9. Jan 11, 2022 #27
    Perchie15

    Perchie15 Light Load Member

    226
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    Aug 16, 2021
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    Thanks all for the help!!! Found a broken wire
     
    Perchie15, Jan 11, 2022
    Perchie15, Jan 11, 2022
    #27
    Goodysnap and Roger McG Thank this.
  10. Jan 19, 2022 #28
    maconhadalata

    maconhadalata Light Load Member

    136
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    Dec 11, 2014
    newark, nj
    0
    mine had the same problem...easy fix
     
    maconhadalata, Jan 19, 2022
    maconhadalata, Jan 19, 2022
    #28
    bad-luck Thanks this.
  11. Apr 13, 2025 #30
    ihc4b

    ihc4b Light Load Member

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    Dec 29, 2021
    0
    I am having the same problem with my mxs in a 2006 Western Star. Fan stays on, but will shut off with a toggle switch I installed to get by with. Had a bad relay in the ac. Ac clutch stayed engaged. No fuse or relay for the ac. Never knew it was the relay labeled for the heater. Ac works great now. Reading this post has given me things to check. I appreciate that? My test light has a volt guage and small led in it. It would not read a voltage, but did have a faint positive light from the led. Can the intake sensor be jumped with a wire for testing?
    The fan overide switch does not affect the fan. How does the fan switch effect the circuit. Does it send a signal to the ecm, or is it in line after the ecm. Should it give a positive or ground? It was a while back when I checked that switch and I can't remember what it did. Thanks in advance
     
    ihc4b, Apr 13, 2025
    ihc4b, Apr 13, 2025
    #30
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