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low pressure air alarm not working properly, ADVICE APPRECIATED

Discussion in 'Trucks [ Eighteen Wheelers ]' started by TowHaul, Dec 17, 2017.

Page 2 of 6
  1. Dec 18, 2017 #11
    TowHaul

    TowHaul Medium Load Member

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    Mar 7, 2016
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    You mean make sure i did not purchase (and install) the wrong one? Why would one be open and one closed? Shouldnt they both operate the same? I was only give 1 part number for bothnprimary and secondary switches by freightliner parts guy
     
    TowHaul, Dec 18, 2017
    TowHaul, Dec 18, 2017
    #11
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  3. Dec 18, 2017 #12
    TowHaul

    TowHaul Medium Load Member

    406
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    Mar 7, 2016
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    I have two seperate guages not dual needle
     
    TowHaul, Dec 18, 2017
    TowHaul, Dec 18, 2017
    #12
  4. Dec 18, 2017 #13
    frt60

    frt60 Medium Load Member

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    May 22, 2014
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    1 sends signal when under pressure other sends signal when low air they look alike only small writing on bottomside of unit easy to get wrong one
     
    frt60, Dec 18, 2017
    frt60, Dec 18, 2017
    #13
  5. Dec 18, 2017 #14
    TowHaul

    TowHaul Medium Load Member

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    So they are seperate part numbers? Both have red band on them and are secondary and primary? Or just primary OR secondary...or neither P or S and instead screws into a seperate port?
     
    TowHaul, Dec 18, 2017
    TowHaul, Dec 18, 2017
    #14
  7. Dec 18, 2017 #15
    frt60

    frt60 Medium Load Member

    312
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    May 22, 2014
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    Yes not at my truck now i carry extra set yes think of break petal step on it swich turns brake lites on.low air loss of pressure turns on lamp. They look the same. Dealer could have grabbed wrong ones . They are marked be the threaded tip on bottom
     
    frt60, Dec 18, 2017
    frt60, Dec 18, 2017
    #15
  8. Dec 18, 2017 #16
    TowHaul

    TowHaul Medium Load Member

    406
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    Mar 7, 2016
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    The low air pressure switch has 10.5 volts going out of it to the dashboard.... i hooked this up to the buzzer and got it to "sometimes work" have to flick the buzzer other times to start it. Also tried splicing off of it to the low air pressure light below dash....light will not turn on as its not 12v to light (10.5). Also bought a relay switch...hooked everything up...the moment i hook a neutral to the relay the volts drop to. 1.26 ....no matter what i do relay never activates power lamp switch. Its a heavy duty relay. ANY IDEAS? I am beyond frustrated
     
    TowHaul, Dec 18, 2017
    TowHaul, Dec 18, 2017
    #16
  9. Dec 18, 2017 #17
    TowHaul

    TowHaul Medium Load Member

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    Mar 7, 2016
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    ...Bueller? ....Bueller?


    could it be that the dash is somehow absorbing 1.5 volts? (chop the dash wire?)

    I thought a relay switch can take a small current (my 10.5 volt) and allow it to open the switch for a much larger current (batter direct connected 12 volts) to relay full 12v to power-on accessories....

    honestly is this forum just full of company drivers with opinions...or are there any of you out there that work on your own trucks and have some basic to advanced mechanical skills? (I have literally NONE but have done a better job at diagnosing/fixing my problems than any advice i have gotten thus far on this forum for any one of the countless breakdowns i have posted regarding this POS truck)
     
    Last edited: Dec 18, 2017
    TowHaul, Dec 18, 2017
    TowHaul, Dec 18, 2017
    #17
  10. Dec 19, 2017 #18
    lilillill

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

    5,642
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    Nov 7, 2007
    Possum Booger, Alabama
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    I will have to look at the schematic when I have gotten some sleep to tell you the exact pin... but basically, the low air buzzer and light are controlled by grounding a pin on the ICU. From memory... Top row, left plug when looking at it as you tilt the cluster out of the dash, third cavity.

    Grounding this pin will make the buzzer and light go out. It sounds like you have a poor ground in the circuit.
     
    lilillill, Dec 19, 2017
    lilillill, Dec 19, 2017
    #18
    TowHaul Thanks this.
  11. Dec 19, 2017 #19
    lilillill

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

    5,642
    13,470
    Nov 7, 2007
    Possum Booger, Alabama
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    Oh... and the two pressure switches are the same for primary and secondary air pressure. Should have a strip of red tape on them.
     
    lilillill, Dec 19, 2017
    lilillill, Dec 19, 2017
    #19
    TowHaul Thanks this.
  12. Dec 19, 2017 #20
    TowHaul

    TowHaul Medium Load Member

    406
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    Mar 7, 2016
    0
    What can i do to test and possibly fix it? I spent 8 hours staring at the cluster and rat nest of wires today. Cobbled something together only to see the volts are too low to consistently activate buzzer and not at all to power light
     
    TowHaul, Dec 19, 2017
    TowHaul, Dec 19, 2017
    #20
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