Where Does Blue Wire of Trailer Wiring 5-Way Normally Run to on Trailer

Question:

The wire set goes into trailer tongue and I see brown green and yellow white come out and run down to the end and to ground on trailer. I see the blue wire go into tongue but I don’t see it exit anywhere to the rear lights or to the brakes? Is the blue wire just not connected in my case? I have a magic trailer that has brakes on it which I think works based on coupler sliding forward

asked by: Mark

Expert Reply:

So the blue wire of the 5-ways like the # A40W5B normally runs to the reverse lockout solenoid of a surge brake actuator like what you described having. The blue wire on the vehicle side of the wiring runs to the reverse light circuit. This allows the solenoid to have voltage when the vehicle is put in reverse preventing the brakes from applying. This runs right to the back of the actuator on the trailer coupler which is why you don't see the wiring ran to the back of the trailer.

expert reply by: Jameson C