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Air trouble: Governor or unloader valve

Discussion in 'Trucks [ Eighteen Wheelers ]' started by tonakis, Jun 27, 2016.

  1. Jun 27, 2016 #1
    tonakis

    tonakis Light Load Member

    284
    103
    Nov 27, 2012
    Fort LAuderdale, FL
    0
    Compressor wasn't kicking in while I started driving yesterday morning, pressure would drop to about 75psi. I stopped, revved the engine - nothing. Then I got rid of some of the air left and it built it back up. Started driving - same thing, pressure dropped below 100psi and the compressor would not kick in. Then after a few of these "stop and build pressure" exercises, it started working fine, it would kick in at 100-105psi to build it up to cutout at 125. From searching online and talking to a couple of people I understand I need an unloader valve. I bought the part and I am waiting my turn at a shop to get it replaced. Is that the part I need or I need a governor?

    Thanks for any help and your time fellas!
     
    tonakis, Jun 27, 2016
    tonakis, Jun 27, 2016
    #1
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  3. Jun 27, 2016 #2
    Ozdriver

    Ozdriver Heavy Load Member

    767
    1,390
    Oct 16, 2015
    Australia
    0
    In my experience, when the unloader valve fails the compressor bumps up to as high as it will go, 150 psi in my case. All you can do is swap over a new governor, and if that's no good it's more likely the unloader. It's a simple job swapping the governor, why don't you do it yourself? Also they are very cheap, an El Cheapo is about $20 or good quality Bendix about $45 (where I live). This is for a Bendix TuFlo compressor.
     
    Ozdriver, Jun 27, 2016
    Ozdriver, Jun 27, 2016
    #2
    tonakis Thanks this.
  4. Jun 27, 2016 #3
    kimbosa

    kimbosa Medium Load Member

    524
    351
    Jul 4, 2011
    lufkin texas
    0
    May be you need that part, but its sounds like some trash was in your lines and by doing the air dump thing you got it out.
     
    kimbosa, Jun 27, 2016
    kimbosa, Jun 27, 2016
    #3
  5. Jun 27, 2016 #4
    Animosus

    Animosus Heavy Load Member

    708
    2,774
    Dec 7, 2015
    SE Wyoming
    0
    The unloader valve can fail in the unloaded state. Usually, I pull the line off the unloader to see if the governor is sending air to it or not when it is below the kick on value. If it is sending air to it you need a governor, if it is not than you need a unloader valve.
     
    Animosus, Jun 27, 2016
    Animosus, Jun 27, 2016
    #4
    tony97905 and tonakis Thank this.
  7. Jul 2, 2016 #5
    tonakis

    tonakis Light Load Member

    284
    103
    Nov 27, 2012
    Fort LAuderdale, FL
    0
    Thanks, guys. I ended up changing both, as I had already bought a new unloader. Bendix governor for $38, unloader valve from Atlanta Freightliner $69. Small shop in Tifton, GA did the job. Problem solved.
     
    tonakis, Jul 2, 2016
    tonakis, Jul 2, 2016
    #5
    Ozdriver Thanks this.
  8. Jul 3, 2016 #6
    Ozdriver

    Ozdriver Heavy Load Member

    767
    1,390
    Oct 16, 2015
    Australia
    0
    With mine, turned out the unloader was absolutely stuffed, but the governor was intermittently playing up so it was hard to diagnose.
    Replaced the unloader, still playing up, even though the old one was stuffed.
    Replaced governor, everything back to normal.
     
    Ozdriver, Jul 3, 2016
    Ozdriver, Jul 3, 2016
    #6
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