Flip open the 7 pin connector cover on your truck
With voltmeter test for 12V DC between pin #4 and pin #1
(4/12V DC-----1/Grd)
RAM ---pin S/B hot
If not check fuse #19 in MAIN Fuse Panel UNDER the hood.
30A Trailer Tow Battery Feed
IF pin #4 is HOT then need to check where trailer umbilical cord connection are made-------access panel on 5vr overhang next to pin box
Truck alternator should 'maintain' trailer battery when truck/trailer umbilical cord connected.
Length of charge line and wire size limits ability to charge a low battery condition
