I'm fairly new at this Rv'n gig and love it. However, when I turn on my hi beams my regular head lights go out. When I turn off my Hi beams my regular head lights come back on. I reached out to my local Thor RV dealer about this and they said "its a Ford issue". I then reached out to Thor Tech support and they stated its suppose to do that. WHAT???.
Now, again I'm new but shouldn't the premise be brighter lights means both teh regular head lights AND Hi beams together create better night time illumination just like your regular vehicles??. Please do share...
I've done the same 'all on' harness on s10's.
I added a light bar to my rv instead of messing with the 5 or 10v backwash voltage and computer crap I might have ran into with the '4 lights on' dongle.
What is happening is the way headlights work, almost always.
Except for older 5 inch round headlight cars and some of the early 4 small square lights I think what you are describing has been standard for many many years.
The hidden light bar wiring instructions is somewhere in my signature thread.
Splitters are available on ebay. You'll need to know h9 from h11 etc.
You will also notice your fog lights won't come on with your bright lights and your(mine) running lights won't come on with your dims.