Trailer wiring issue. brake light and turn signal don't work with head light on

[booblinker]

The brake light and turn signals work when the headlights are off, but when I turn the headlights on, the turn signals and brake light no longer do anything, it just stays lit. Trailer lights are 2 wire, dual filament, and ground to frame.

 

[Captain Ledd]

2 bulb? (red+reverse) or 3 bulb? (red+amber+reverse)

If it's the 97 (which should still be 3 color) I'd say something is shorting out between wires that run to the brake lights, jumping onto the others making them all just stay on when the tail-lights come on.

Do they change brightness if you step on the brake pedal?

My bet is frayed/shorted wires or the little adapter harness itself is toast.

 

[booblinker]

Single bulb, two wire, grounds to frame. Brand new wiring and lights on trailer, new trailer wiring and convertor on truck. I've been told I probably hooked the taillights to the bright filement, and the brake/turn signals to the low filement. We will see when I get off work tonight and swap the wires.

 

[Captain Ledd]

Single bulb, two wire, grounds to frame. Brand new wiring and lights on trailer, new trailer wiring and convertor on truck. I've been told I probably hooked the taillights to the bright filement, and the brake/turn signals to the low filement. We will see when I get off work tonight and swap the wires.

Ah, yes that will do it as well.

As for 2 bulb or 3 bulb I was referring to the lights on the truck. If the wires were shorting to each other it would still blink if you turned the signal on with the 2 bulb tail-lights because the tail light itself would blink.

 

[TomB1269]

Looking at it from a schematic point of view, I think you may have switched ground and headlight.
If Headlight and turn are hot w/o ground, light goes out. Headlight cold & Turn hot, lights on.
If ground was headlight hot, then when headlights off Turn/brake would light. When headlights hot, turn/brake nothing as the ground side of the turn/brake would be hot and therefore no voltage difference no current flow in bulb.
If weak ground turn/brake will tend to pulse very weakly. Also if I am correct when Turn/brake is on & lights off you may see a dim glow from running/marker lights, and when headlights are on the markers will be full bright.