I want to add a switch to an existing fuel heater for my diesel engine. The system currently has a thermostat automatically sensing when to turn on the fuel heater in winter conditions. However, it only works when the key is in the "ON" position. I want to add a switch to manually turn this heater on without having to insert the key and turn it on. But when I flip the switch off I do not want to to completely cut power to the system, I want the system to go back to it's self regulating "Auto" mode.
To simply, it should act much like a modern day home thermostat. You can turn the fan on manually and it will run continuously or you can turn it to "auto" so the system manages it. At no point does that switch completely turn off the system (that is done with a separate "heat/cool/off" switch.
The switch I want to add should function like the first switch allowing for "on/auto" mode.
