How to Test a Central Digital Thermostat


Central digital thermostats give you the power to control your furnace or air conditioning unit's temperature. If your furnace or air conditioner is not working, perhaps your thermostat is not working. Testing your central digital thermostat not only allows you to narrow down the causes of heating or cooling problems, but can also maximize your unit's efficiency. Run a few tests to see if your thermostat is properly functioning.

  • Check the settings on your thermostat if your heater or air conditioning unit is not turning on. Make sure it is on and set to "Heat" or "Cool."

  • Turn off your furnace or air conditioner if your thermostat is not turning on. If your central digital thermostat is battery operated, remove the old batteries and insert new ones.

  • Adjust the temperature on your thermostat from low to high if your furnace or air conditioner is still not functioning. While you are adjusting the temperature, have a friend or family member stand at the furnace or air conditioner. Ask your helper to listen for sounds. If a sound is heard when you turn the thermostat's temperature up, your furnace or air conditioner is getting a signal; however, it may be damaged.

  • Turn off your furnace or air conditioner and remove your thermostat's cover. This may involve pulling it off, depending on the model. Refer to your thermostat's manual if you are unsure how to remove the cover. Remove the screws on the sub-base. You should see two or four wires coming from a hole in the wall. The wires are connected to screw terminals on the sub-base. Four wires indicate your thermostat is connected to a furnace and central air conditioning. If only two wires are present, those are for the furnace.

  • Inspect the connections and write down where all wires connect so you do not forget.

  • Connect the "R" (or Rh) wire to the "W" wire to test the heater. Turn on your furnace and listen for any sounds. If the furnace starts up, your thermostat is faulty and needs replacing. If the furnace does not turn on, check the circuit breakers inside an electrical panel in the attic, basement or electrical room. Once you locate them, turn the circuit breakers off and on again to reset them.

  • Reinstall your thermostat's cover. If your furnace or air conditioning unit is the problem, contact a qualified technician.

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