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No a/c fan running constantly

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Rig Wrench, Jul 23, 2011.

Page 1 of 2
  1. Jul 23, 2011 #1
    Rig Wrench

    Rig Wrench Medium Load Member

    398
    66
    Dec 24, 2010
    northeast
    0
    Got an 07 Western Star, no A/c and the clutch fan stays engaged all the time, I have power to the fan solenoid at the firewall, and if I put an additional ground on it, it functions properly. Cant get power to the a/c clutch at all, system is full, all high/low switches are signaling properly, and all fuses are good. Now I notice the cab blower motor runs on low even with the switch off???? Is there anything that would disrupt all these funcions? I have tore into the the harness and cant find any bad wires or connections. any help would be greatly appreciated
     
    Rig Wrench, Jul 23, 2011
    Rig Wrench, Jul 23, 2011
    #1
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  3. Jul 23, 2011 #2
    Sparkz

    Sparkz Light Load Member

    76
    16
    Jul 10, 2011
    New Zealand
    0
    What engine?
     
    Sparkz, Jul 23, 2011
    Sparkz, Jul 23, 2011
    #2
  4. Jul 23, 2011 #3
    DL550CAT

    DL550CAT Road Train Member

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    Oct 18, 2009
    Waynesburg, Pa
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    My first tought would be the high pressure switch is stuck but that would not explain the blower fan. You say the high and low switches are functioning properly how do you know for sure?
     
    DL550CAT, Jul 23, 2011
    DL550CAT, Jul 23, 2011
    #3
  5. Jul 24, 2011 #4
    Rig Wrench

    Rig Wrench Medium Load Member

    398
    66
    Dec 24, 2010
    northeast
    0
    Engine is an NXS Acert. The owner had it hooked up by his engine guy and he said the switches were recognized and functioning properly, I could see him being wrong though. Just seems strange cause without the jumper ground wire the fan runs constantly, regardless of weather the a/c is turned on or off.
     
    Rig Wrench, Jul 24, 2011
    Rig Wrench, Jul 24, 2011
    #4
  7. Jul 24, 2011 #5
    Sparkz

    Sparkz Light Load Member

    76
    16
    Jul 10, 2011
    New Zealand
    0
    Don't get to work on the yellow stuff, so can only comment on how other engines behave.

    If the inputs are correct, I would disconnect the ECM connector and ground the fan solenoid wire with a test lead. Be VERY CAREFUL not to expand the terminal in the connector. If you can operate the solenoid it probably means that the ECM fan output has failed.

    It is possible that the blower fan always runs on slow with the ignition on. This pressurises the cab to help keep dust out. Another possibility could be a stuck relay.
    Has any work been done on the truck recently?
     
    Sparkz, Jul 24, 2011
    Sparkz, Jul 24, 2011
    #5
  8. Jul 24, 2011 #6
    billandlori

    billandlori Medium Load Member

    357
    107
    Sep 5, 2010
    Stratford, Ontario, Canada
    0
    If you have the rear HVAC fan on, the dash one will run on low speed even if the switch is in the off position.

    Bill
     
    billandlori, Jul 24, 2011
    billandlori, Jul 24, 2011
    #6
  9. Jul 24, 2011 #7
    Pablo-UA

    Pablo-UA Road Train Member

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    Oct 11, 2010
    Borispol, Ukraine
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    I found one thing with a/c of freightliners and WSs. If there is no refrigerant ore pressure switch is bad, fan runs all the time becouse there is signal on engine ECM input (fan auxially on). if I disable this input reprogremming ECM when I fix A/C - no fan is on when A/C is on!!!!!
     
    Pablo-UA, Jul 24, 2011
    Pablo-UA, Jul 24, 2011
    #7
  10. Jul 24, 2011 #8
    Rig Wrench

    Rig Wrench Medium Load Member

    398
    66
    Dec 24, 2010
    northeast
    0
    I know the system is full, i'll see about getting the high pressure switch replaced, I was told it was functioning but, the system was almost empty so I'm not sure I can believe that.
     
    Rig Wrench, Jul 24, 2011
    Rig Wrench, Jul 24, 2011
    #8
  11. Jul 26, 2011 #9
    Sumothertrucker

    Sumothertrucker Light Load Member

    92
    16
    Jan 10, 2011
    I c corn
    0
    I would start by jumping the high pressure switch with a paper clip. Should be the reddish colored one up by the radiator. Just unplug and insert in the connector. If your fan immediatley kicks out, you have a bad switch. Also if the fan runs constantly it will not allow the low pressure switch to let the A/C compressor kick in however it should still kick in very briefly but won't be enough to give you any cool. Try that. you may be dealing with 2 seperate problems
     
    Sumothertrucker, Jul 26, 2011
    Sumothertrucker, Jul 26, 2011
    #9
  12. Jul 26, 2011 #10
    Rig Wrench

    Rig Wrench Medium Load Member

    398
    66
    Dec 24, 2010
    northeast
    0
    what if its a 3 wire switch?
     
    Rig Wrench, Jul 26, 2011
    Rig Wrench, Jul 26, 2011
    #10
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