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I'm having trouble with my trailer break lights working when the truck lights are on. With the truck lights are OFF all trailer signals, caution lights, and break light work. When the truck lights are ON the trailer running lights, signals, and caution lights work, but the break lights do not work. I also hooked the trailer up to a Honda and had the same problem. Thought it was the trailer wiring, but just redid the whole system and still have the same issues. Any suggestions?
Try http://www.etrailer.com/faq-wiring.aspx. This should help. Make sure the lights and trailer are grounded. Especially with a tilt trailer. The tilt pins carry the ground. Run a ground strap from the frame to the bed.
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Hello. It seems there is an electrical 'break' between the electrical jack of your truck and trailer. This could be the jack itself or a broken wire(s) of the trailer. Good luck and keep me informed; if you want to.
There is a tail lights fuse for the truck, but not for the trailer.
First, check that your left tail light on the truck is working, if not fix the problem (new bulb, bad contact, fuse).
Then the obvious suggestions regarding the trailer are: Check the tail light portion of the bulb to be sure it is not blown. If good (best to put in new one to be sure), then check the wiring from the front of the trailer all of the way to the non working bulb, including every connection and at any place it is secured to the trailer frame. If all is good with the trailer circuit and bulb, then check the truck's trailer connector, including any adapters. If by chance the truck is wired with a flat 4 wire harness the problem may be solved (but usually the blinkers are the problem). Modern trucks require a 5 wire harness which self adapts to the standard 4 wire trailer circuit. Check for dc power (12 volts) from the truck's female connector. One wire will be ground, others will be taillights (turn on headlights), brake lights (have someone press brake pedal), and blinkers (turn on switch and blinkers).
Have you checked the bulbs? Some people don't beleive all the lights can burn out at once but when one brake light is on they are all on and for the same amount of time.
If the bulbs are fine then check the connection where the trailer plug is to the main harness. Some of those connectors go between the main harness and the tail lights and the connector can go bad.
Check the plug at your gmc outlet, your right signal wire has been damaged before the plug somewhere. If you have a test light switch your right signal on and make sure it is working at the plug on your gmc, you will find it is not working, than trace the wire back from the plug till you find where it has been damaged or you can run a wire straight from plug to your right signal.
If the brake light is working on the sierra, Check the right light in the left break socket. If that is good then. I would check continuity between the connection to the light on the trailer. Remember to always disconnect anything you are trying to check continuity or you may get a false reading. if that's good, check your power at the source where they first separate to go to there respective lights. Always trouble shoot from where you have power then go to next connection point. this should get the issue narrowed down.
it seems you have a short in either one of the lights or interlock. all are connected to the same fuse. trace the wiring from the fuse box back to the component. Using a test light test in between the wires. check for any obvious breaks in the wiring.
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