The car output relay module auto on after vehicle successful ignition and turn off automatically after turn off the Engine. This will auto on the devices after you start engine and off the devices automatically after engine stop. No modifiction required and ideal to protect battery from low voltage.
Module factory has built a complete set of testing procedures, can automatically identify 12V or 24V car without adjustment, usually only connect wire input and output load. If the factory settings on your car does not work, please follow following method to manually identify system voltage,