Why does the MaxTow gauge have to be connected to a 12 volt constant source aswell as a 12 volt switch source?Updated 3 months ago

The gauge needs to be connected to a 12v constant source in order to keep the memory of the last brightness level you set. The 12v constant wire also is for the back lighting of the gauge so if you do not care about the gauges memory and the last brightness you set you can connect it to the 12v switched wire.