hows it going I put a flatbed on my truck and am having a hard time wiring the lights. I put on led lights (tail lights). so heres what its doing when i have the truck off and the lights off the tail lights work when i push the brake. next i put on the marker lights they all work and the tail lights come on (half bright) then when i push the brake the go one full. all works as it should then i put on the full lights (head light) and i get the same results everything works as it should... then when i put the key in and turn it on the tail lights get full power as if the brake was on all the time. there are 3 wires coming off the tail light theres a ground, run, and stop and turn. i do not have the turn signal hooked up to them at all. anyway im lost on what to check next any help?? ive heard a few things about getting a diffrent relay when going to leds but dont know
thanks mike

 

sounds like something is grounding out somewhere maybe?

 

FYI there was a thread on here a few days ago that had the led's causing automatic trans shifting problems. Not any help otherwise..

 

My Dad was a Ford tech for many years, we had a conversation about this a while back. A guy brought a truck into the dealership with shifting problems and no cruise control. Dad worked on it and it turned out the problem was the LED tail lights that the guy had put in his flatbed. When the key is on and the PCM is on, it sends out a trace voltage to check the integrity of the circuit. If the resistance of the lights is too low, it will cause them to light up. This also happens on our 2011 GMC work truck with a service body, when it is dark you can see the LED lights lit up very faint. Anyways, if the computer sees voltage coming back though the circuit because it has not dropped due to resistance, it will assume that the brakes are applied (whether they are or not). Since it assumes that the driver is riding the brakes, it will not activate the cruise control, and it will change the shift pattern in an automatic. Same thing happens if you put an LED bulb in the 3rd brake light on top of the cab. There are companies that make resistors that you can put in series with your LED lights so that they will work properly, just search on Google for them. Hope this helps a little...

 

That is a very good explanation why this type of problem occurs. Reps sent ...