I have done LED taillight conversion on my XJ. The LEDs are wired directly to the factory wiring.

SST - is wired to Stop and Tail
Side Marker - is wired to tail
Amber Turn - Wired to Turn signals
Independant 55 watt reverse lights (Reverse lamp line powers a relay from main power)

All grounds to respective grounds for that socket

Tested everything long ago and all lights activate and work great. I also have done the replacement to electronic flasher to stop fast blink.

I picked a set of tow lights that I was going put on a hitch basket for better visibility. While testing the lights I noticed something weird. For one they don't work. Turn makes both light blink, brake doesn't work, only tail. But i have not tested them outside the vehicle yet.

The strange thing is what I noticed when checking the brake signals . I jammed the brake pedal, and checked the lights.

I noticed my LED turn signals (On my XJ) were lit, very dimly, but they were lit . If I disconnected (changed the load characteristics) the tow lights and reconnected the lights the lights changed intensity, or when out, or went on.

To summarize:

My LED turn signals come on slightly when I press the brakes.

Messing with the trailer converter load casues them to change behavior (brightness, if they are on, etc) in some way. But they will light without anything connected.

Turn signals still work and light and fully extinguish when the turn signal is activated. Afterwords they go back to being dimly lit.

I was wondering if anybody has ran into this with LED taillights before? I have not investigated yet. I don't have the model trailer converter, and I haven't investigated the trailer converters wiring (I will) . Just checking.

Thanks