Interior lights run on the house battery.. Which SHOULD be charged by pins 1 (Ground) and 4 (12 volt aux) on the 7 pin umbilical cable.
However not all Tow Vehicles are shipped with that lead enabled (Fuse or relay missing) and it is SUPPOSED to only provide power WHEN THE ENGINE IS RUNNING.
If the house battery is DEAD or Disconnected it will not light internal lights.
THIS. has nothing to do with running lights but it is also a safety issue because if tow vehicle and trailer part company.> The brakes on the trailer are engaged BY THAT SAME HOUSE BATTERY so check it out. (NOTE It may charge even if the disconnect is active (Disconnected) or not depending on disconnect. Brakes should bypass the disconnect but again, Some after market disconnects affect those as well.. next page Running lights
They work off the Tow Vehicle only, save for pin 1 (Ground) they have NOTHING in common with the interior lights.
Same for brake and turn lights.
