On an old car, when the ignition switch is turned off, then everything is really turned off. There is no draw on the battery- things are OFF! New cars are different. With multiple computers and loads of sensors and electrical stuff there is always something ON, maybe on a reduced level but still ON! This is why battery life on new cars is reduced.
This is not true. Several circuits are still "hot" and if they develop a fault they can cause trouble. On Mopars, horn, brake lights, hazard flashers, dome lights, glove box/ trunk/ underhood light and the output circuit of the alternator.
