Advice for Rewiring Trailer to Clear Up Wiring Issues Where Brakes Lock Up and Pulsate with Blinker

Question:

Hi I have a 2005 Chevy 1500 with a seven pin connector but is set factory for 4 way. Now I have a seven way car trailer and have put the wires were the scematics tell me to. I also have a trailer brake unit mounted in truck and set in the plug under dash. I am trying to get both working in conjunction with one another. No dice! Truck has turn and brakes together. When applying brakes trailer goes good but when turning signals on trailer brake is at full and pulsates with signals on truck. I am wondering if you could help me with this situation. Upper wires are connected to studs in conjunction with seven way wire. Box from left to right is ground white, clearance yellow, left turn red, stop black, brown right turn and I have my blue running to brakes but is on aux stud because of turn signal issue. Trailer is 1978 and has a black and white together for ground and power to brakes , a green, a brown, and red. And a black for power to 12v

asked by: Lee B

Expert Reply:

The immediate brake lock up of your trailer brakes that also pulsates with the blinkers is a clear indicator that your turn signal stop light circuit is getting applied to the brake output circuit.

You mentioned a separate signal for the brake lights on the black wire of the box. Does your tow vehicle have separate turn signals from stop lights as well? Or is there a converter on your trailer like part # 118158 to convert the signal?

Your best option is going to be to use a circuit tester to test the circuits of the connector of your tow vehicle to determine all of their functions and then be sure that the wiring to and from the junction box matches this. I attached a wiring diagram that shows all of the circuits for you to check out as well.

expert reply by: Jameson C