Why Is My Gas Furnace Making a Clicking Noise and Giving Me No Heat?

We see several homeowners asking this question: “Why is my furnace making a clicking noise and not producing heat?”

We’ll explain.

Most likely, your furnace is making a clicking noise and not providing heat because your furnace’s spark igniter is trying to ignite your pilot light or burners but is failing to do so.

In other words, there’s an ignition system malfunction that needs to be fixed. Otherwise, your furnace won’t start.

Before we get into more details, we need to say that this is an issue that an HVAC technician needs to handle. (Sorry DIY folks, there’s not much you can do here.)

If you live in the Atlanta area, contact Coolray for furnace service.

Now, if you want to understand the problem further, read on. We’ll explain:

• What an ignition system is
• Common issues with the ignition system that cause the constant clicking noise

What is an ignition system?

Just like how your car’s ignition system starts your car, the furnace’s ignition system starts (“ignites”) the furnace burners, which heat your air. 

If the ignition system does not work properly, then neither will your furnace. 

To put the ignition system in context, here’s your furnace’s order of operation:

1. Your thermostat calls for heat.
2. The induced-draft fan motor energizes, pulling air up into the burner.
3. The draft switch closes to prove the draft fan is working.
4. The ignition system is energized for approximately a minute.
5. The gas valve opens.
6. The furnace burners light.
7. The furnace blower comes on after a delay of a few minutes and starts distributing air throughout your home.

As you can see, if there’s a malfunction at step 4, your furnace won’t open the gas valve, and the burners won’t light.

Now, let’s talk about that clicking noise. The click is the spark caused by a spark igniter, which is used in 2 common ignition systems:

• Intermittent pilot ignition—Uses a spark igniter to light the pilot flame, which then ignites the burners.
• Direct spark ignition (DSI)—Uses a spark igniter to directly ignite the burners.

Each of these ignition systems can have issues that will cause the spark (the “click”) without igniting the burners.

Let’s talk about those ignition system issues, shall we?

Common problems with ignition systems

Thermocouple issues

A thermocouple is a flame sensor that, when it detects a pilot flame, opens gas valves to the furnace burners. However, if the thermocouple is malfunctioning or covered in soot, it won’t sense the pilot flame and shut the gas valve. The spark igniter will spark (click) for about a minute trying to ignite the flame. 

Pilot light/flame issues

The pilot flame may not be hitting the thermocouple properly due to an incorrect mixture of gas and air. Again, if the flame sensor thinks the flame isn't lit, the spark igniter sparks again and again until it gives up. 

Gas valve isn’t energized 

No gas = no ignition. So if the gas valve is shut, the spark igniter has nothing to ignite and just keeps sparking. Some causes of a shut gas valve include:

• Bad ignition board
• Bad connection between the board and the valve
• Bad valve

All of the above are issues a furnace technician needs to fix. 

Need professional furnace repair?

If the clicking noise persists or your furnace is still giving you no heat, we can help.

Contact Coolray for a furnace repair. 

Coolray has locations in metro Atlanta, Nashville and Birmingham, AL. Have more questions? We’d be happy to help – just contact us online.