Switchin shouldn't be a proble
As long as your switch doesn't cross the Off position when switching, you should be fine. That's why most selector switches don't rotate a full 360 degrees, but are arranged Off-1-Both-2 without allowing the switch to continue from 2 to Off. If you notice a interruption to the power on your devices when switching across the 1-Both-2, it probably won't hurt the equipment, but I would replace the switch, because what will be damaged is the diodes in your alternator (if the engine is running). You have to be able to switch among 1-B-2 after you've started the engine in order to charge the drained battery. Hope this clears things up
