Back in trouble again. Turn signals in rear now not working or brake lights. the one on top of the roof is working. What is going on? Have grounds to lights.

 

The front parking and turn signals light up and work but flash fast. When I pull on the 4 way flashers the front turn and parking unit flashes regularly. I ran another ground from the battery back to the rear lights. Now that makes no difference. There must be a problem somewhere up front? Running lights work properly in back and front also.

 

And the reverse lights work just fine so the grounds for the lights must be good.

 

The schematic shows the common elements of your symptoms to be the turn signal switch, hazard switch or a issue with the connectors and/or the wiring harness.
Just because some of the lights work does not eliminate the possibility that part of the switch is bad. There are multiple elements to the switches, dirty contacts in the switch may prevent some lights from working while letting the other lights work.

 

Hi everybody. I have been on a 5000 mile trip across country with the Suburban. I left with my wonky tail light issues. When I made it to Texas i had a few days to look over my issue again. After several hours of cleaning and e installing new grounds every where I found them. I removed the trailer light wiring harness and of course the same issues. So the next day we were on it again. By mistake my brother in law was holding one of the rear tail light assemblies while connected dangling there low and behold the turn signal stopped and started working as he moved the light assembly. Well it turns out the cheap Chinese tail light assemblies from O Reilley's the body shop installed for me are total junk. My factory wiring plug fits into the assembly well but the connector from the light are too big to allow the truck harness a positive good connection. We could wiggle the light assembly and the turn signal would work then not. I found 2 factory taillight assemblies in a junk yard in Texas installed them and now no issues. Drove all over and problem solved. So take away from this is cheap Chinese parts again. I thank all the forum for all the guidance I received and appreciate it, Don.