I have an '05 F150 SuperCrew 2WD, and I bought the LED brake light/signal light for my truck. Now, it's got the flat 4 prong trailer plug, and the new LED strip has the mating connector. Now this is where it gets tricky, I plug the LED strip into the existing plug on the truck, and the strip lights up, but the light comes on as if the brakes are being applied, when they are NOT, and when I turn the blinkers on, the dash indicator just stays on and there is no flashing of anything. Now, I disconnected the brake wire (brown) from the 4 (white, yellow, brown and green), and now when I turn the lights on, there is no running light, but everything else seems to work properly (brake light comes on when the brakes are applied, and both blinkers, including the hazards function properly). I then ran a wire directly to the running light wire on the tail light, and now the lights (running light, brake light) both work properly, but when I try to turn on the signal (either one) it goes back to the original problem of no flashing of the lights and a constant brake light......any ideas? Any and n all accepted and appreciated. Thank you in advance.

 

If your truck plugs work right send light strip back . Try it on someone else's truck?

 

yeah.. use a test light or multimeter to verify the 4 pin on the truck is working properly.. like Redfish says.. You could have a bad strip..

 

Can you possibly tell me what the multimeter should read when testing the plug on the truck?

 

Just set it to test continuity