After wiring for trailer lights (all working fine) my 2001 Chevy has no dash lights, radio, clock, or other similar lights when turning on the headlights. All lights work when the headlights are off. All other lights, dome, front, read, break, etc.. work fine. Just the dash lights don't work ony when turning the headlights on. btw, all this is when not connected to the trailer.

I checked every fuse I could find. Don't know how to check the relays.

Anyone have thoughts on this? If it is a relay, how would I check it or which one?

thanks; rjr