Just traded my 04 Ford F-150 crew cab 4x4 for an 04 Dodge Ram 2500 Cummins 4x4 CrewCab. Towed a 5th wheel with the Ford, no problems with the lights. I had a 5th wheel hitch and plug put into the Dodge last week, and we're heading out tomorrow with the trailer. We were checking the lights, and found that the brake lights on the trailer don't work, but yet the turn signals, hazards, and parking lights all work...everything works on the truck...any ideas??? We've checked all the fuses under the hood, as well as tried the factory installed plug in the bumper. Please help! I don't have time to take it back to the place that installed the hitch! Thanks!!!

 

take a test light and have your buddy pump the brakes see if you get power if not look underneath maybe a wire isnt connected if it is start tracing wires

 

check the bulb. maybe it's busted.

or it could be a bad brake light switch. They are easy enough to check with a test light.

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BMW 740IL Brakes | BMW Z3

 

make sure you have a good ground at the ball. alot of trailers get their ground off the truck and if you have a new hitch that is freshley painted this paint will stop the ground from the receiver to the ball.

 

If the newer trucks have the same setup as the older Dodges, it doesn't have a ground at the back of the truck. My guess is whoever set up the lights for you didn't do the brake light wire correctly. If I'm not mistaken, there are four wires, one of the brakes, one for each turn signal, and one for when the head lights on on. I can't remember the exact color, but the brake light wire should be on one of the ends of the light plug in if it's a four pin plug. But as others have said, check all the wires with a test light.

 

The signals and the Brake lights are on the same wires for each side the only seperate brakewire isfor the trailer brakes. I'd make sure the brake lights on the truck work too. if not then the only thing left is the trailer light bulb. i work on this stuff for a living and this is a fairly common problem with the trailers