When you unlock the doors the interior lighting is supposed to come on so you can see what you're doing in the dark just like all vehicles do nowadays. I now have to manually turn the knob to laminate the cab and when it first went out my I awoke to a dead battery since I wasn't used to manually turning it off when I exited the vehicle. Since after you lock your doors the lights stay on for a minute then slowly dim and turn off. Very easy to overlook leaving the knob turned in the on position.