Outside brake lights illuminate in cold weather issue [Solved]

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Houle Truck Trans LLC, Oct 28, 2020.

  1. Houle Truck Trans LLC

    Houle Truck Trans LLC Bobtail Member

    Oct 28, 2020
    Last year I had an issue where the brakes would come on all by themselves (only below 20°), causing me to pull over and not let me go anywhere. I thought it was water so I would turn my truck off, drain the tanks, and the lights (outside) would turn off until I built full pressure (which took forever). I took it to Peterbilt (2016 Peterbilt 587) in which they diagnosed the problem as a brake switch (not the problem). I spent $2200 for this repair (in which I thought was fixed) and I didn't have any problems as it was warming up since winter had passed. Well, this winter the same thing happened but at least I knew a work around to get me to a shop safely (drain tanks, start truck, and hold protection valves pushed in, and go before pressure builds up). I couldn't find ANYTHING about it online given the symptoms (outside brake lights illuminated, front brakes locked, only below 20°, brakes unlocked after draining tanks). I even tried alcohol in the tanks; didn't work. Was told it could also be brake pedal plunger not sliding back into place, tractor/trailer protection valves, or abs valve clogged, or even adaptive cruise sensor fault. Took it to a TA in Cheyenne where they knew what was wrong. It was the air dryer filter; full of water; frozen. $200 filter and I was on my way with a symptoms-free truck in single digits temperature. Hopefully this finds it's way to someone else with the same problems and can spare them the agony of throwing parts at it to fix.
    bigguns, xsetra, daf105paccar and 2 others Thank this.
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  3. kemosabi49

    kemosabi49 Trucker Forum STAFF Staff Member

    Jan 13, 2013
    SW Arkansas
    This is one of the most neglected items on trucks. Changing the desiccant filter every year can keep you from dealing with water in the brake line issues.
  4. stillwurkin

    stillwurkin Road Train Member

    Dec 2, 2017
    Happy you found the issue. Change filter on air drier at least every fall. 200 bucks is quite expensive for a filter. Most are a spin on/ off filter nowadays.
  5. daf105paccar

    daf105paccar Road Train Member

    Apr 15, 2012
    In certain climates ,changing the airdryercartridge 2 times a year will save you money.
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