Electrical – switch two 12v sources with 5 pin relay


I'm installing a stereo in an RV and would like to maintain default behavior of having the stereo receive power on vehicle accessory power/ignition, but also be controlled by a switch in the RV for use when the vehicle is not in use. These are the requirements:

  • When the RV switch is OFF, the stereo turns on and off with vehicle accessory power.
  • When the RV switch is ON, the stereo remains powered regardless of vehicle operation.
  • The source of power when the vehicle is running does not matter, but it must utilize the RV batteries when it isn't.

Would there be any problems with utilizing a ~30A 5 pin relay to achieve this? The stereo utilizes an external amp, so it will be drawing very little power.

12v 5 pin relay power supply switching

Best Answer

It will work just as you have it drawn. But why not just use a SPDT switch to switch between house power and accessory power? Simpler, cheaper, more reliable, no down side immediately apparent...