Hoping for some help.

With the truck off.. My roof marker lights and dually fender lights work fine.
With the truck on.. They do not come on. Switching between "auto" and "on" on the light switch gets the fender lights and cab lights to flash quickly.. but they never stay on.
I turn the truck off... turn the light switch to on... and they come on and stay on.. \\

Help would be appreciated!

Mark

 

Did some more troubleshooting...
If I unplug two of the fender lights.. things work as expected..

I hooked up my trailer and everything is fine there as well with all 4 fender lights plugged in.

Still Baffled..

 

Did you ever figure anything out on this? I’m having the exact same issue.

 

im having the exact same issue. Anybody figured this out?