trailer light issues

Discussion in 'Chevy Truck Talk & GM News' started by wolfmann, Jul 26, 2012.

  1. wolfmann

    wolfmann Member

    I have a 04 silverado equipped with the factory towing package. I have recently discovered that when the trailer is hooked up and the truck is off, the right tail light is still on. The parking lights are off. Also when t turn on the right turn signal on the trailer flashes both lights like I have the hazard flashers on. At first I thought it was the trailer, but I hooked it up to my other truck and it works fine. So I checked th trailer plug on the truck and repaired a couple wires that the previous owner tapped into for led light bar, thinking this was the problem. Repairs complete and retested and still the same problem. Now I'm really confused. So I checked the trailer light fuses on the side of the dash, they are fine. I am going to be pulling a trailer on vacation and I need to get this fixed before I leave. The trailer has a four pin flat connector and I am using the factory adapter that came with the truck. Any help would be helpful :neutral:
  2. dpeter

    dpeter Epic Member 5+ Years 500 Posts

    Is this trailer/truck new to you? I ask because people can get pretty creative when left on there own and not conform to anything close to the accepted standard. There are some diagrams in the towing section of the forum that will help get it sorted out. Either on of the three is not standard or two of the three is not as in the old truck and trailer are wrong but have been made to work together or the new truck just ain't right.
  3. wolfmann

    wolfmann Member

    I have had this truck and trailer for about 4-5 years and had used them together for years it just started this. Wondering if corrosion got somewhere in the wiring.
  4. wolfmann

    wolfmann Member

    Although I will check to make sure the wires on the trucks plug haven't been changed and i just haven't noticed this before thanks
  5. dpeter

    dpeter Epic Member 5+ Years 500 Posts

  6. pmf608

    pmf608 Epic Member 5+ Years 1000 Posts

    When it comes to trailer wiring, really strange things can happen when a ground is bad on the trailer. When I was fixing one of my stepdad's trailers, the ground from the trailer plug to the frame was bad and since all of the lights ground through the frame to that wire, it made weird things happen.

    For example, when I turned on the left signal light, it flashed all of the trailers parking lights and backfed through my truck to light up half of the LEDs for the turn signal in my passenger side mirror. I knew that all of the wiring was correct when this happened, and once I sanded the rust and everything off of that ground, everything worked fine.

    So, my advice would be to check all of the grounding points on your trailer if this is a new problem that just started. Unbolt them, sand them to bare metal, and put them back.
  7. dpeter

    dpeter Epic Member 5+ Years 500 Posts

    Given that this combo has been working and now is not, I completely agree with pmf608. Missing grounds are bad enough but the intermitant and poor ground are truely bizzare.
  8. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Check the ground wire continuity on the truck.

    I suggest this, because, you have tried the trailer on an other truck and the lights appear to be ok.

    The truck ground is connected to the truck frame and the trailer ground is usually connected to the trailer frame; however, there is also a ground wire in the truck/trailer connection. If the ground wire is broken/bad on the truck, the trailer will try to ground through the ball. Not normally a good ground.
  9. Sierraowner5.3

    Sierraowner5.3 Epic Member 5+ Years 1000 Posts

    i agree with rayvoy, that is a very likely case.

  10. wolfmann

    wolfmann Member

    ok i have checked the trailer wiring and rewired the damn thing just to be sure. i also ran a secondary ground to the trailer from the truck, and have the same results, works great with my 97 silverado but the right tailight stays on with the truck off and when you hit the left turn signal the right side binks as well when the trialer is hooked to the 04 silverado. so i went ahead and unplugged the wiring from the back of the trailer light harness of the truck and tested the wires with a multimeter and the trailer is doing exactly what the truck is telling it to do????? somnething is crossing in the wires but is only flowing enough volts to make the taillights p.o.'ed.... i pulled the wiring for the hitch off the truck (as much of it as i could) and cannot find any corrosion, cuts or other defects, so i tested the trailer turn fuses and the problem and before that cause im getting the same readings. as i mentioned before im taking a trip to TN in a few weeks and if i have to i will hardwire a for way trailer plug into the tailights but i REALLY do not want to do that! im just wondering where this problem is and where to check for it, the only places that i can figure is the flasher unit, or the multifuntcion lever on the steering collum, but i think that i would have other issues if it were either of those items.

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