How to Test a House Thermostat

How to Test a House Thermostat

Heater or AC on the fritz? It could be your thermostat, not your system. Though yours may have been around since your home was built, home thermostats don’t last forever. Determine whether the issue with your system is simple thermostat malfunction, learning how to test a house thermostat with the help of Air Serv.

Signs Your Thermostat May be Bad

If your thermostat is unlit/unresponsive and its batteries are fresh, your system won’t turn on (or conversely, won’t turn off), or the actual room temperature is nowhere in the vicinity of your thermostat’s temperature setting, your thermostat could be bad.

How to Check a Thermostat Step-by-Step:

If you’ve checked the obvious, ensuring your thermostat is ‘on,’ has fresh batteries, a breaker has not been tripped, and the thermostat is set to the right mode (heat/cool) and proper temperature, and your system still does not work, you’ll need to test the thermostat wires to confirm thermostat function.

  1. Turn off your heating or cooling system.
    Do this at the circuit breaker box.
  2. Carefully remove the thermostat cover to expose the wires.
    Prying it off carefully and gently with your hands.
  3. Remove red and green wires from the terminals on the thermostat.
    The red and green wires typically power the AC. Unscrew the wires from the terminals. Grip the wires tightly to ensure they don’t fall within the wall cavity.
  4. Twist red and green wires together to test the fan.
    Wrap the wires together.
  5. Turn the system back on.
    Turn the power back on at the breaker box.
  6. If the fan turns on when you restore power, the thermostat is bad.
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  7. Repeat the same sequence with the red and white wires.
    This tests the heater/furnace. Again, turn off power at the breaker box. Connect the red and white wire, then restore power to test. The same rules apply here – if the fan turn on when power is restored, you need a new thermostat.
  8. Do not touch the red and yellow wires together!
    The yellow wire that connects to the thermostat controls the compressor – a very expensive component of your system you do not want to 'fry' when you return power to the thermostat wiring.

When to Call a Pro

Messing with wires can be dangerous – to you and your system. If your wires aren't the typical colors, or the mere mention of the words 'wiring' and 'breaker box' make you break out in a sweat, you may be in over your head. To avoid system damage and a potentially expensive repair bill, it's best to contact a trained HVAC professional for help with a simple thermostat function test. Should your thermostat prove to be bad they can also help you choose the best replacement option for your home, budget, and lifestyle.

System down? It may be time for a new thermostat. Get your system back up and running in a flash, improving efficiency and performance with the addition of a new smart programmable thermostat, quickly installed by your friendly area Aire Serv® pro today.