I have a 2006 freightliner Columbia. Here’s the problem. My right tail light on my tractor was bad. It was giving me a turn signal but no running light. Went to the shop and got a new one (LED) . 20 mins after putting it on . My LEFT turn signal didn’t give the indicator inside (on dash) but it was working. Next day was different. Left turn signal was only working with my lights off. If turned them on the left turn signal would not work but the four ways work normally. I only changed the right side tail light. And started giving me issues. I bought all new lights so they match , bought a new harness and a new turn signal switch and still nothing. I also checked the fuses and are good ( also before I changed to all new tail light the tail light on the left was always an LED. The right side one was non LED
Check the ground connection. Better, ground each light to the truck or trailer. Shouldn't matter if you mix LED and incandescent lamps. Good luck
It may be a flasher issue. With a mix of incandescent and LED’s If you don’t have a heavy duty “electronic” type flasher designed for LED’s and one rated for 10 lamps/ lights or more they will give odd intermitted service.
