A properly working non-programmable thermostat is the key to keeping a home at a comfortable temperature. As a thermostat ages, it can become less reliable. The dial on the thermostat may no longer work correctly, or the thermostat may not read the temperature accurately. This can make a difference in energy bills and a home's comfort level. When the thermostat stops working correctly, it is time for a replacement.
Switch the circuit breaker to the cooling and heating unit to the off position. Turn the thermostat to the on position and check the cooling and heating unit. If the unit does not power on, the electricity to the thermostat is off.
Remove the thermostat cover and locate the wires to the thermostat.
Label each of the wires, using the labels provided with the new thermostat. Spread the wires apart so they do not fall inside the wall while you are working.
Unscrew the screws holding the back of the thermostat on to the wall, using a Phillips-head screwdriver. Remove the back of the thermostat from the wall.
Position the base of the new thermostat against the wall where the old thermostat rested. While holding the thermostat base against the wall, place a level on the top of the thermostat to ensure the base is even.
Place a pencil through the mounting holes in the base and make a small mark on the wall. Remove the base from the wall.
Make two holes through the pencil markings with an electric drill.
Push the wires for the furnace through the holes on the back of the thermostat.
Drill the back of the thermostat on to the wall, using an electric drill and screws provided with the thermostat.
Attach the front of the thermostat to the base of the unit.