I have a 1996 cherokee I replaced my front wiring harness because I was having problems with the turnsignals after I replaced it all the turnsignals and markers work great they just dont light up when I have the headlights engaged I purchased the harness online and when it arrived at my house it had a different connector for the side marker than my jeep so I replaced it with the correct pigtail when I purchased the harness I hadn't realised it's for a european cherokee could that have something to do with it

 

Have you read this thread? I ran across it yesterday, and it seems it's relevant here.

https://www.cherokeeforum.com/f2/how...nction-249610/

One thing that stood out to me was the point someone made about LEDs causing the turn signals to work (but in a different pattern) but markers not turn on with headlights. Did you install LED bulbs?

 

I hadn't read that thread before thank you and no I haven't installed LEDs its all stock lighting

 

Weird. Yeah, maybe it is from differences between european and north american harnesses. I don't know much about it myself - hopefully someone else pipes in or you find a lead in that thread.

 

I'm betting you're missing the ground connection, and the signal lights are grounding though the headlights when they're not powered. Do the markers work if the headlights are unplugged?