*Brian,
I believe there is a thermal overload built into your light switch. This would act just like you describe.
This thermal is there to protect the light circuit from excess current draw. It appears yours is "overloaded" and is tripping the breaker.
This circuit should only react to headlights and taillights. Is everything wired correctly...the dimmer switch included.
Is there a wire slightly pinched up near the cowl or where it goes from left side to right side. Maybe a wire mashed and partially grounding in the loom to the rear of the truck. Is there a light that doesn't work, or is dim?
The other option would be a defective aftermarket light switch. Maybe the switch came from China and they had to use an old razor blade for the thermal contact.
This is protection, and it's doing its job! You have something drawing too much current and will have to find it.
Stuart
