If your water heater has stopped heating, a tripped thermal switch may be to blame. In water heaters and many other types of home appliances, thermal switches disrupt power to the appliance's heating mechanisms when the appliance starts to overheat. Most thermal switches are triggered when the temperature of the water in the tank rises above 170 degrees Fahrenheit. While resetting the thermal switch on your water heater will allow it to operate again, the thermal switch may continue to trip if the underlying problem is not solved.
Look for a rectangular control circuit panel on your water heater. Depending on which brand and model of water heater you own, the control circuit panel may be located on the back or side of the appliance.
Locate your water heater's thermal reset switch or button. The thermal reset is usually a red or white switch or button at the center of the control circuit panel.
Reset the thermal switch or button on your water heater. If your water heater has a thermal reset switch, flip it. If your water heater has a thermal reset button, press and hold it for up to 4 seconds to reset your appliance.