So I am having a weird light problem with my truck and trailer. Truck is a 2004 Chev, 8500 Single axle dump. With Cat C7. Trailer is a 10 Ton, Towmaster tag, Air breaks. About 6 years old. Problem is When you plug the trailer lights in all the clearance light come on! On the truck and trailer.:Banghead Then when you unplug them they all go off. The truck and trailer have always done this before but Only when you would turn the lights on in the truck. They would then stay on until you unplug the trailer or press the light interrupt switch on the dash. Then they would stay off. Now they stay on all the time when the trailer lights are plug in. They are a little dim unless you turn them on in the truck then they light up normal. Where should I start with this problem Thanks.
Have you put any LED bulbs in the trailer? I had this same problem with a CAM trailer with LED bulbs.
Have you taken the male and female plugs apart and checked for corrosion, broken wires etc.? Its probably the best place to start. Somehow, power is getting back into the clearance light circuit from a hot wire in the plug.
I have had mirror lights come on dimly when switch was off. It was a bad ground. Check your grounding. It can cause weird problems.
another thing to try is hooking up to a different trailer. That would isolate the fault to your trailer, not all the wiring circuits completed when you plug a trailer in.
Yes I did put two LED in but, that was a while ago. Did your problem start as soon as you installed them or later on?
I Had the male plug apart. I fixed a couple of connections that looked questionable. I Then ran out of time and did not check the Female. When I get a chance I will check that out.
Its the ground, its always the ground!
I did almost nothing but chassis electrical repair for a few years, and everytime something really strange happened, it was the ground. I would try hooking it to another trailer to see if the problem was w/ the truck or trailer. A bad ground will frequently cause the wrong lights to light up in response to the controls. Good Luck P.S. don't forget to let us know what you find
Run a jumper cable from the frame of the trailer to the frame of the tractor and see if that fixes it. If so you know its a ground problem.
When I used LED lights in my VW dune buggy the only thing affected was the flasher for turn signals. I had to buy an electronic flasher because of the difference in resistance. I don't think that LED's would be causing your problems.
Good idea for where to start, but I would not give up on grounds if that doesn't fix it. I would think it's more likely to be the ground from the socket to the truck, but wouldn't be suprised at it being anywhere.
I think so. My problem was that with the headlights on, the running lights would flash. I didn't notice it for a long time since I rarely towed anything at night. There is a different impedance between the LED bulbs and the incandescent bulbs. My trailer came with LED lights. Most of the vehicles that have this problem with LEDs are foreign, BMW and MB. The answer is very easy. There is an extension cord for 7 pin round connectors that matches impedance. As a really quick test, I would try putting incandescent bulbs in.
Yep ground is the problem most of the time but the last place most people look.
Alright I think I found my problem. There is a connector not far after the connection at the truck. It had some corrosion in it and when it pulled apart the prong for the blue wire broke off. So I pulled the broken part out and put it back together and all the lights worked! So my next question. Do I need the power from the blue wire for anything? It has power going to it all the time. The only thing that I can think of that might need power would be the abs for the brakes.
blue wire The blue wire is 12v constant for ABS purposes.