A Whirlpool water heater uses a thermostat to regulate the amount of time its heating element runs, not the element's temperature. Each water-heater element has its own thermostat—so the elements work independently of each other. A Whirlpool thermostat contains two parts: the temperature-setting bottom half and the high-limit control switch, the top half of the thermostat. The high-limit control switch turns the temperature-setting half the thermostat off if the water temperature rises above 170 degrees F. Whirlpool sets the thermostat at 120 degrees F at its factory.
Turn off the Whirlpool water heater's circuit breaker. The water heater uses a double-pole circuit breaker labeled "Water Heater." A double-pole circuit breaker looks like two circuit breakers mounted together with one switch.
Remove the two screws that hold the thermostat's access cover to the water heater with a Phillips screwdriver. Each access cover, located on the side of the water heater's tank, covers a thermostat and an element.
Set the cover aside. Move the insulation that covers the thermostat and element.
Pull the plastic protective shield from the thermostat. The protective shield snaps into place. Save the shield for later installation.
Inspect the thermostat and the wires. The numbers printed on the thermostat identify each terminal. To aid the installer, the wires use color-coded insulation.
Tag each wire with masking tape and write the terminal's number on the tape with a pencil.
Loosen each terminal screw on the old thermostat with a Philips screwdriver. Pull the end of each wire from its terminal.
Slip a slotted screwdriver between the metal clips and the side of the thermostat. Pry the clip away from the thermostat and pull the thermostat away from the tank. The metal clips grip the sides of the thermostat near its bottom.
Align the new thermostat with the metal clips and snap it into place. Once the clips grab the thermostat, wiggle the thermostat around slightly. This verifies the thermostat's back rests tightly against the tank.
Loosen each terminal screw on the new thermostat with a Philips screwdriver. Do not remove the screws.
Push each wire into its respective wire terminal and tighten the screws with the screwdriver. The numbers on the wire's tags should match the number printed next to the terminal it connects to.
Align the round hole in the protective shield with the red button on the high-temperature limit switch. Push the shield against the thermostat until it snaps into place.
Replace the water heater's insulation. Hold the access cover over the thermostat and push the screws into their holes. Tighten the screws that hold the thermostat's access cover to the water heater with the screwdriver.