Originally Posted by Dave_Monica
I seem to recall others mentioning having to add a fuse in the fuse panel to have power on the #4 pin (black wire) which would be the 12V power to the camper's battery. Perhaps your owner's manual covers it. Dave
Since the Original Poster (OP) did not mention which tow vehicle he has (either in signature line or profile), (that I found anyway), I am going to take a chance that it is a Chevy/GMC product and attach the information on how to "hot up" the trailer charging line that is disconnected from the factory. You may need to buy a 10mm nut with lock washer (M6 Fastener) to finish the install.
Since my 2008 GMC 2500HD came with the heavy duty tow package and the 5th wheel wiring harness, I expected it to be ready to tow. I was mistaken and needed to do the following to get the charging circuits ready.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW