10 Reasons Why Your Furnace Is Making a Clicking Sound

Furnaces typically operate quietly. When the furnace initiates a heating cycle, you’ll hear a sound, then the whooshing noise of air blowing through the vents will last for several minutes. At the end of the heating cycle, the blower winds down and the sound stops. If you hear clicking sounds, they may be normal under certain circumstances, but in other cases, they suggest a problem. Let’s take a look at 10 reasons why your furnace is making a clicking sound and when you should reach out to a technician for troubleshooting and repairs.

1. Spark Igniter Fails to Ignite the Burner or Pilot Light

When your thermostat sends a signal to the furnace that it needs to initiate a heating cycle, the first step involves the blower drawing air into the combustion chamber. Next, the spark igniter or electronic ignition ignites the pilot light or burner. The ignition makes a clicking sound when it turns on. The sound comes from the two pieces coming together to make a spark. Under normal operating conditions, you should only hear one click at the start of the heating cycle. If you hear several clicks in a row, then the igniter is having difficulty creating a spark or getting hot enough to ignite the gas.

2. Thermocouple Problem

The thermocouple is a sensor that detects flame in the combustion chamber. Once it senses the presence of a flame, it opens the gas supply valve, which allows the furnace to burn fuel. A faulty thermocouple may not sense the flame. This will prevent the flow of gas into the combustion chamber. The igniter may continue to click because there is no remaining gas to create a flame. Faulty thermocouples require professional replacement.

3. Stuck Gas Valve

Corrosion, a crack or other damage may cause the gas supply valve to get stuck. If the valve is stuck in the closed position, gas will not flow into the combustion chamber. This prevents the furnace from maintaining a flame and burning the fuel. The igniter will keep clicking because the thermostat will continue signaling it to start a heating cycle. Malfunctioning gas valves require identification and repair or replacement by an HVAC technician.

4. Improper Mixture of Gas and Air

The combustion chamber must maintain the right mixture of natural gas and airflow for the fuel to burn. Repeated clicking may result from the flame not reaching the gas. If there is too much airflow, it might blow out the flame, so the igniter will keep trying to light the gas. If there is too little airflow, the flame may die out. This will also cause the igniter to keep trying. Too little gas flow also inhibits the maintenance of a flame, and the igniter will continue attempting to ignite the burner or pilot light. Too much gas flow may cause tiny explosions and popping sounds.

5. No Gas Supply

If the gas pipe or valve are not energized with a gas supply, the igniter will continue attempting to create a spark. Furnaces have their own connection to your home’s main gas line. You may need to check your other gas-powered appliances to see if they have a supply of gas. If your oven’s gas burners work and your gas-powered water heater or clothes dryer are operating properly, then the problem is with the furnace’s connection. If other gas-powered appliances in your home are also malfunctioning, then your gas pipe may have a problem that requires prompt repairs.

6. Cold Ignition Flame

The temperature of the ignition’s flame must be just right in order to ignite the gas. If the flame is burning at too cold of a temperature, the igniter will keep clicking because it’s not burning the gas. The igniter may click endlessly because the thermostat will continuously communicate to it that a heating cycle is required. An HVAC technician can adjust the flame controls to correct the temperature of the igniter’s flame.

7. Damaged or Broken Fan Blade

The furnace blower has a fan. This fan spins and propels air into the combustion chamber. If your furnace is part of a forced-air system, it may have a second fan in the air handling unit. This fan blows the heated air through the ducts and into the rooms of your house. A bent or warped fan blade may cause a clicking sound with each revolution of the fan. Because the fan spins at a high rate of speed, you might hear a lot of clicking for the duration of the heating cycle. Debris stuck in the blower can also make a clicking sound when the fan’s blades hit it. A broken fan blade could cause parts to become loose. When the other blades hit the loose parts, they could make a clicking sound.

8. Contactor or Electrical Malfunction

Some furnaces use electrical contactors to create a spark. If the contactors get stuck, they may continue clicking without creating a flame. Furnaces also contain wiring and connections from the circuit breaker to the furnace control panel and the fan motors. If a wire becomes loose, the vibration from the fan may create a clicking sound. Clicking sounds may also indicate another electrical malfunction. These issues require prompt professional attention. If you have an electric furnace, the clicking sound could come from the heating elements. Dust or debris on the heating elements may burn off and create a clicking sound. A crack in the heating element may also make unusual sounds during heating cycles.

9. Worn Bearings

Furnace inducers have bearings. After many years of regular use, the bearings may wear out. A few skipped annual tune-ups may also allow debris to build up around the bearings. Rust buildup on the shaft of the bearings may also make a clicking sound, especially if flakes of rust interfere with movement. Regular lubrication and cleaning of the bearings and shafts prevent premature wear and tear. Using a furnace with worn-out bearings may cause the motor to overheat and fail.

10. Debris in Ducts

If you can hear a clicking sound during a heating cycle, but the sound is not coming from the furnace, it might originate within the ducts. A seam between two segments of ductwork may be loose. This could cause the two pieces of metal to rub against each other and make a clicking noise. Debris stuck in the ducts could also create a clicking sound when the heated air travels through the system. Items stored too close to metal ductwork may have shifted or come into contact with the metal, and the clicking could be the sound of the two items hitting each other as the motion of the air moves the ducts.

In addition to furnace repairs, we also offer air conditioner repairs and heating and cooling maintenance, replacement and installation. Our ductless mini splits, air duct sealing, duct cleaning, dryer vent cleaning and attic insulation services keep your home’s air cleaner, healthier and more comfortable. For more information about furnace clicking sounds or to schedule an appointment with a service technician, reach out to us at Quality Air Of America.

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