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What Can Cause a Furnace to Stop Working?

For a long time, furnaces have proved to be a reliable source of indoor warmth. They offer a cozy and comfortable feeling that adds life to your home. However, issues may arise and cause your furnace to stop working, leading to a cold, uncomfortable house.

Before you embark on seeking a solution for your non-functional furnace, it’s essential to understand how it works, its model, source of power, and other factors. The primary sources of energy for furnaces are fuel oil, gas, and electricity. By understanding how yours functions, you can start investigating the issue from there or hire a professional HVAC company to help you out.

Attic Furnace Install and Maintenance

Dirty Burners

The burners in a furnace are prone to dust and dirt collection after a while. The debris reduces the heat coming out through the burners, worsening the issue as the dirt increases.

The first thing is to turn it off or disconnect it from the power source. The next step is to detach the burners from the primary system and clean off the dirt using a soft brush and vacuum. You should ensure that each part is clean and that all the debris is eliminated.

Faulty Igniter

Faulty igniters are the leading reasons why most furnaces stop working. When that part of your heating system is spoiled, the fuel fails to ignite even after turning on the furnace. You can check the state of your furnace’s ignition system by placing a multimeter on the plug. A zero reading confirms that you need to repair or replace it, while other readings show that the igniter is not responsible for the failure of your system.

Poor Thermostat Settings

Your furnace operates under the control of its thermostat. If you forget to set it on, the communications or heating commands will not be relayed to the heating system, preventing ignition.

Avoid this by checking the settings and categories that you had previously selected. Ensure that the furnace is set to heat mode with a heat range above the room’s temperature to create and maintain the heat cycle. It’s also essential to confirm the state of your thermostat’s batteries and whether they need cleaning or a replacement. Finally, check if the breaker could have tripped and interfered with the circuit, especially if it’s hardwired.

Air Filter Clogged

When the filter gets clogged, the air gets restricted from the circuit and causes the system to overheat. The safety switch senses the extreme temperature changes and shuts down the furnace to prevent damages. You can avoid this by checking the air filter from time to time and getting the debris out of it or replacing it with a new one altogether.

AC Unit Inspection & Repair

Circuit Breaker

The furnace can stop working if the circuit breaker flips because it prevents power circulation to the heating components. If you ignite the system and realize that the heat is not coming up, you should investigate the circuit breaker’s position and reset it if it’s flipped. If the problem persists, you can consult a technician to check the issue professionally and fix it after making the diagnosis.

Some tanks have failed within a couple of years due to wearing out and accidents in some scenarios. This is very common when undersized expansion tanks are installed in homes and due to other plumbing failures.

Whether you are looking to install an expansion tank on your water heater or you need to replace your existing one, we here at Absolute Airflow can help. Please contact us today to learn more about our plumbing and HVAC services or set up a maintenance appointment with our team of skilled technicians.

Dirty Flame Sensor

The flame sensor is a vital determinant of your furnace’s functionality. It relies on the igniter and pilot light to initiate the flame and keep the fuel burning. Once it accumulates debris, the flame sensor loses its ability to detect the flame and uphold combustion, prompting your furnace to stop functioning. It would be best to clean the sensor using a soft brush or cloth to maintain its abilities.

Cracks in the Heat Exchanger

The system’s heat exchanger facilitates heat transfer from the combustion chamber to the surroundings. It is prone to damages such as cracks and breakages as time goes by. These cracks lead to carbon monoxide accumulation, which can leak into the house and cause health issues. When a crack in the heat exchanger is found, this will lead to the unit’s replacement.


A well-lit and heated space is essential, especially during the cold seasons. Having a functional furnace is a necessity, but it can inconvenience your household if it stops working. Routine check-ups are important to discern the possible issues and revert accordingly.

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Customer Reviews

Called Absolute for my 81 year old landlord in the height of Summer heat. Scott came out to inspect the old beast of an AC and found many issues. He took the time to educate us, note everything, photograph it and provide several recommendations...and my stubborn landlord has done nothing LOL. A couple months later we asked that Scott come back out and he was there that same day.

Emily H.

Santa Ana, CA

I contacted Absolute Airflow to check my mother's AC, as it was not getting cold. The tech (Scott) arrived earlier than his scheduled time, and was very knowledgeable, professional, and most of very personable with my mother in letting her know that the issue was. Superb customer service Scott and thank you Absolute Airflow! I highly recommend Absolute Airflow.

Billy A.

Billy A.

Bellflower, CA

I have called in Absokite Airflow for my tankless water heater and A/C unit for maintenance. They were professional and took the safety precautions necessary including wearing a mask and cornering their shoes when entering my home. I recommend them highly. Shout out to Zack who took care of the tankless water heater.  They were professional and friendly.

Beatriz S.


Santa Fe Springs, CA

Carlos came to our house to access the A/C project and to give us an estimate. He was very knowledgeable and took his time to explain all the opinions in detail as well as the installation process and warranties. Tanner and Chris were the installers, they were very professional taking their time and attention to details. To keep our house clean while installing the new A/C system.

Robert M.

Robert M.

Whittier, CA