Does your thermostat make a clicking sound? It’s a common phenomenon associated with both old and new thermostats alike. You may be lounging in your living room, only to hear a clicking sound coming from the thermostat when your furnace or air conditioning system turns on.
In most cases, a clicking sound is normal. Thermostats will often make a clicking sound when they activate the air conditioning systems or furnaces with which they are used.
Relays and Clicking
If you hear a clicking sound coming from the thermostat, don’t panic. It’s probably just the relay. Thermostats work by opening and closing a circuit in response to the temperature for which they are set. Relays are devices that control these circuits.
To activate your air conditioning system or furnace, the thermostat must close the circuit. This is where the relay comes into play. Also known as a relay switch, it will move in response to the thermostat’s temperature setting. If the thermostat determines that it’s time to run your air conditioning system or furnace, it will move the relay so that it closes the circuit.
You won’t be able to see the relay. Relays are found inside of thermostats, so they are covered by the housing unit. But the relay will move automatically in response to the thermostat’s setting. As it moves, it may open or close the circuit. Relays are designed to control the circuit for air conditioning systems and furnaces so that thermostats can activate these systems.
What About Mercury Thermostats?
Even older, mercury-based thermostats make a clicking sound. Mercury-based thermostats use a mercury bulb to activate air conditioning systems and furnaces. The mercury bulb will move in response to the thermostat’s settings. Depending on the direction in which it moves, the mercury bulb will then activate the appropriate system while simultaneously creating a clicking sound.
New thermostats typically feature a relay, whereas mercury thermostats feature a mercury bulb. Regardless, you may hear a clicking sound as they activate – as well as deactivate – your air conditioning system or furnace.
While some sounds are a sign of an underlying problem with a thermostat, clicking is not. It’s normally for thermostats to make a clicking sound. If it’s particularly loud, you can always move the thermostat to a different part of your home, or you may be able to add insulation to it. But you don’t have to worry about a clicking sound harming your heating, ventilation and cooling (HVAC) system.