Older homes often have decades-old thermostats. You can replace them, but you have to disconnect them from your heating and cooling system first. If your current thermostat is faulty, you could save yourself hundreds of dollars on energy bills by installing a new one. Luckily, thermostat wiring is simple and you can remove your old thermostat in no time. However, you must take a few safety precautions so you do not hurt yourself or damage your home.
Turn the electrical power off to your furnace and air conditioner. You can do this by flipping a breaker or removing the service fuses.
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Remove the cover plate from your thermostat. A typical thermostat has a simple plastic cover that pops off to reveal the wiring and other components, though you may need a screwdriver to pry it off carefully.
Disconnect the exposed wires leading into the wall from their terminals in the thermostat. Make a note of or mark the wires with tape to remember where they were attached.
Unscrew the thermostat mounting case from the wall. Slowly remove the remaining parts of the thermostat and let the wires slide out the hole in the center. Be careful not to let the wires slip into your wall. You can twist the wires around a pencil or other object to prevent them from coiling into the wall.