If the water heater is a Suburban, the 12 volt switch for the gas mode and the 120 volt switch for electric mode are both fixed at 130 degrees, and no adjustment is possible. On the Atwood water heaters, there is an adjustable thermostat available that goes from 110 degrees to 150 degrees, part number 93105,
https://www.rvpartsnation.com/rv-wat...-heater-parts/ . We have the Suburban and just mix cold with hot and have no issue with doing this.