Don't know about other years, mine is always hot, key on or off, doesn't matter. What is supposed to happen in tow mode or with the headlights on, is the alternator will kick up the charge rate to help charge the battery on the trailer. How well it works, I don't know. We usually have electric most places we camp, so the converter most likely does most of the charging.
2013 Starcraft Travel Star 229TB
2011 Jayco X17Z(traded in)
2010 Jayco Jay Series 1207(traded for the 17Z)
2011 Chevrolet Silverado 2500HD Z71 CC 6.0L/3.73
Reese "Pro Series" 800lb Trunnion WDH w/sway control