Hi johnrivers77,
Welcome to the Heartland Owners Forum and to the family. We have a great bunch of folks here with lots of information and all willing to share their knowledge when needed.
The switch with the red handle that lights up is for the Electric Water heater element. Always make sure you run water through the water heater to be sure it is full of water before you turn the switch on. The electric element will burn out if not in water.
You say light above it...now that I don't know for sure. My next guess would be something for the Yetti system if you have that. Hopefully one of our Gateway owners will jump in and help out.
Enjoy the forum.
Jim M