Glad you tracked down the problem...
I am surprised that the dealer would not have hooked up your battery before you left the dealership...
Your trailer is equipped with electric brakes and has the trailer disconnect connection in case the trailer becomes disconnected from your truck going down the road. It will pull this disconnect cable plunger out and will immediate apply electric brake actions on all your electric brake wheels. The 12VDC power for this operation comes from your trailer battery. This is also a DOT requirement to have this installed and operational.
By DOT RULES you must have all of this hooked up when towing your trailer...
Perhaps only the large cable going to the trailer converter was not connected up and one of those other two wires that was were connected actually goes to the trailer disconnect switch...
Just adding some info for future towing of your trailer. Must have battery connected (by DOT LAW) to operate the trailer electric brakes if needed.
just my thoughts
Roy and Carolyn
I claim Horse Creek Country in Southern Ill - Momabear is from North Texas
We live in King George VA
RETIRED DOD DOAF DON CONTRACTOR Electronics Tech 42YRS
"We're burning daylight" - John Wayne
2008 STARCRAFT 14RT OFF-ROAD POPUP with PD9260C and three 85AH 12VDC batteries
2010 F150 FX4 5.4 GAS with 3.73 gears - Super Cab - Towing Package - 2KW Honda EU2000i Gen
K9PHT (since 1957) 146.52Mhz
"We always have a PLAN B"