Why Does The Flame On My Furnace Keep Going Out?

furnaceflame Cappy Heating and Air Conditioning
furnaceflame Cappy Heating and Air Conditioning from cappyheating.com


Dealing with a furnace that keeps shutting off can be frustrating, especially during the cold winter months. If you’re experiencing this issue, it’s essential to understand the potential causes and find a solution to keep your home warm and comfortable. In this article, we will explore the common reasons why the flame on your furnace keeps going out and provide some tips to help you resolve the problem.

1. Dirty Flame Sensor

A dirty flame sensor is one of the most common reasons why the flame on a furnace may go out. The flame sensor is responsible for detecting the presence of a flame. Over time, it can become covered in soot, dust, or debris, causing it to malfunction. Cleaning the flame sensor with a soft cloth or emery cloth can often solve this issue.

2. Faulty Thermocouple

The thermocouple is a safety device that senses the presence of a flame and sends a signal to the gas valve to keep it open. If the thermocouple is faulty or worn out, it may struggle to maintain a stable connection and cause the flame to go out. Replacing the thermocouple is usually the best solution in this case.

3. Clogged Air Filter

A clogged air filter can restrict airflow to the furnace, leading to overheating and the flame going out. Regularly replacing or cleaning the air filter can prevent this issue and ensure proper airflow to the furnace.

4. Gas Supply Issues

If the gas supply to your furnace is interrupted or inadequate, it can result in an unstable flame or cause it to go out completely. Ensure that the gas valve is fully open and that there are no issues with the gas line or supply. If you suspect a gas supply problem, it’s essential to contact a professional technician to address the issue safely.

5. Blocked Venting System

A blocked venting system can cause improper air circulation and prevent the furnace from functioning correctly. Debris, bird nests, or ice can obstruct the venting system, leading to the flame going out. Regularly inspecting and cleaning the venting system can help prevent this issue.

6. Malfunctioning Limit Switch

The limit switch is a safety device that monitors the temperature inside the furnace. If the temperature exceeds a certain limit, the limit switch shuts off the gas supply to prevent overheating. A malfunctioning limit switch can cause the flame to go out unexpectedly. Consulting a professional technician to replace the limit switch is recommended.

7. Improper Gas Pressure

If the gas pressure is too high or too low, it can affect the stability of the flame on your furnace. A qualified technician can check and adjust the gas pressure to ensure it is within the manufacturer’s recommended range.

8. Ignition Control Module Issues

The ignition control module is responsible for initiating the furnace’s ignition sequence. If it malfunctions or fails, the flame may not ignite or go out shortly after ignition. Replacing the ignition control module is necessary in this scenario.

9. Electrical Problems

Faulty wiring, loose connections, or other electrical issues can disrupt the proper functioning of your furnace and cause the flame to go out. It’s crucial to have a qualified professional inspect and repair any electrical problems to ensure safe and reliable operation.

10. Lack of Maintenance

Regular furnace maintenance is essential to prevent issues like a constantly extinguishing flame. Neglecting routine maintenance tasks, such as cleaning, lubricating, and inspecting the furnace, can lead to various problems. Scheduling annual maintenance with a licensed HVAC technician can help identify and resolve potential issues before they become major problems.


A flame that keeps going out on your furnace can be a sign of various underlying issues. By understanding the potential causes and following the tips provided in this article, you can troubleshoot the problem and ensure your furnace operates efficiently and reliably, keeping your home warm and comfortable throughout the winter season.