You will know very quickly, if the switch is still on, and the brakes are activated. They will drain the battery in a VERY short time, and you won't have any 12v lights (unless you are plugged into 120v). Had a fellow camper deliberately pull his pin, on a rental pop-up, because that's what he said that he was told to do to set the parking brakes during the 15 minute orientation that the rental company gave him....
Be Safe, and Everyone Goes a Home,
2014 RAM Laramie 2500 w/6.7L Cummins Diesel and Automated Safety Hitch
2016 377RLBH Jayco North Point
300W of Suntech Solar w/Rogue MPPT Controller & Xantrex 2000W PSW Inverter