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New LED tail lights , couple of the diodes dimly lit when everything is off.

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Green461, Sep 3, 2019.

  1. Sep 3, 2019 #1
    Green461

    Green461 Light Load Member

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    Mar 22, 2019
    Southern WI
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    Truck is a 2001 KW T800, added new tail lights (LED) and noticed a couple of them very dim when off, it is only the ones hooked up to the turn/brake circuit. I tested the wire coming from the left/stop and the right/stop and they have 2.3 volts coming from them. All parking lights, hazards, turn signals, brake lights function as normal. A friends freightliner century does the same thing, I noticed last year and asked him why his tail lights stay on but very dim, LED's as well.

    Anyone ever come across this or have an idea whats causing it?
    Thanks.
     
    Green461, Sep 3, 2019
    Green461, Sep 3, 2019
    #1
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  3. Sep 3, 2019 #2
    Cattleman84

    Cattleman84 Road Train Member

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    Do they stay on dimmly, even say 24 hours after turning everything off?... Do they run the battery completely dead?

    If NOT, there could be a small capacitor in the circut somewhere that the LED lights will take a while to completely drain. If they DO stay on until the battery goes dead then I'm not sure what would cause it.
     
    Cattleman84, Sep 3, 2019
    Cattleman84, Sep 3, 2019
    #2
    Bean Jr. Thanks this.
  4. Sep 3, 2019 #3
    uncleal13

    uncleal13 Road Train Member

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    I’ve seen that.
    In my case one time I had loose wires in the 7-pin connector of the light cord. The set screws weren’t tight enough.
     
    uncleal13, Sep 3, 2019
    uncleal13, Sep 3, 2019
    #3
  5. Sep 3, 2019 #4
    Green461

    Green461 Light Load Member

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    Mar 22, 2019
    Southern WI
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    They stay on for more than 24 hours. This is a truck I just built, stretched, made into a flatbed. The factory tail light harness was cut and then ran to a box where they were attached to terminal strips so everything is neatly laid out and no splices anywhere. So if isolated its the harness that comes from the front of the truck somewhere. I have not traced that yet. Could a brake switch, the pressure switch that activates the tail lights be messed up? contact inside of it partially making contact? But then the cruise control works so I'd think if there was a connection in there it would kick the cruise off and not enable it. ?? High idle does not work on the truck though, using the cruise switches it will not come on. Im still thinking this through, I am hoping someone else had the same issue. I will look for the pressure switch to see if any voltage is coming from it tomorrow.
    Thanks.
     
    Green461, Sep 3, 2019
    Green461, Sep 3, 2019
    #4
    Oxbow Thanks this.
  7. Sep 3, 2019 #5
    Roberts450

    Roberts450 Road Train Member

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    My 2018 pete dose this too, will turn a couple LED’s on in the tail lights on the tractor and the trailer if hooked to one with LED’s when the door is open and key off or when the key is in the on position no matter weather the door is opened or closed.
     
    Roberts450, Sep 3, 2019
    Roberts450, Sep 3, 2019
    #5
    Oxbow Thanks this.
  8. Sep 3, 2019 #6
    BoxCarKidd

    BoxCarKidd Road Train Member

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    I saw some 9670's that would sweep the tach and or speedo with the turn signals. They had a twist together multi pin connector near the RF cab hinge. They would get water in them and track voltage between the pins.
    Also have seen a single strand of wire out of place in a connector like unclean13 mentioned,
    Maybe check for voltage at the 7 way connector on rear of cab. If present then go to the turn signal switch. Test it and or unplug it. That will narrow your search down some.
     
    BoxCarKidd, Sep 3, 2019
    BoxCarKidd, Sep 3, 2019
    #6
    Oxbow Thanks this.
  9. Sep 3, 2019 #7
    spsauerland

    spsauerland Road Train Member

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    The brake lamp switch for brakes is separate from one used for cruise/Jake's/Engine ECM.
     
    spsauerland, Sep 3, 2019
    spsauerland, Sep 3, 2019
    #7
    Oxbow, BoxCarKidd and Green461 Thank this.
  10. Sep 3, 2019 #8
    starmac

    starmac Road Train Member

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    I don't think it will be a problem with an 06, but could be.
    On some older trucks I have had trouble when I installed the last led light, some I could get everything to work until I turned on the headlights, some would even work with the lights on, but cause problems when the high beams were on.

    If you are using the tractor tail light circut, the brake and turn signals supply currant to the same wire, do you have the flasher that has an extra ground wire for led lights? Sometimes you also have to use the pigtails thave have a resister in them too. I have also just wired in an invisible regular bulb for stop and turn, for resistance when all else failed, it isially just takes one for one side. Don't ask me why. lol
     
    starmac, Sep 3, 2019
    starmac, Sep 3, 2019
    #8
    Oxbow and Green461 Thank this.
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