Is a ground always a ground?
I think I know the answer to this, but want to make sure. I have a 2018 Siesta 24ST, and I've installed a dvr connected to the original rear and side cameras and a new front camera. All is powered by the + and - wires to the harness for the original camera switcher box, and the power goes off and on with the ignition switch. (I believe only the + wire is switched, and the - wire maintains continuity.)
I want to add an "on/off/on" toggle switch that would allow me to switch the system to the larger bank of coach batteries, so the system can run while the engine is off, for security when I'm away from the coach, or to record through the night. I believe I need only to connect the positive wire from the harness through the switch, and run another positive wire from the coach batteries to the switch. Then I can select either"off", "on" through the ignition, or "on" all the time from the coach batteries. I believe the negative or "ground" does not also have to be run from the coach, because both the chassis and the coach batteries share a common "ground" even though they are two separate battery systems. Is this correct? Thanks.