furnace ignite

If you want to be warm and cozy while it’s freezing outside, you need a furnace that works properly. Nevertheless, many homes experience the common and unpleasant problem of a furnace that refuses to light. In cold weather, this issue can quickly escalate from a small inconvenience to a major crisis.

In this article, we’re looking at the top 5 reasons why your furnace won’t ignite and how you can deal with those issues.

1. Faulty Ignition System

Furnace ignition system problems are among the most typical causes of ineffective ignition. Electronic ignition methods are more dependable and efficient than traditional pilot lights and are mostly found in contemporary gas furnaces. But these systems can go down, just like any other part, and cause the gas furnace ignitor to not work well.

Two modes of operation are available for the ignition system: a hot surface ignitor that glows red hot to light the gas, and an intermittent pilot light that employs a spark to start before the main burners ignite. Both kinds may have problems usually as a result of the system’s electrical components wearing down or failing.

When the furnace’s electronic ignition system stops working, the blower can turn on as the furnace tries to start, but you won’t hear the familiar clicking sound of the ignitor. If you don’t hear a clicking sound, it’s likely because the ignition system isn’t getting power or isn’t working properly.

Dealing with a faulty electronic ignition system in your gas furnace

Expertise from a licensed HVAC technician is usually necessary when diagnosing and fixing ignition systems due to their complexity. To make sure the ignitor is getting power, the technician will inspect the ignition system for any indications of wear and tear and check the electrical connections.

In addition, they might look for obvious indications of wear and damage in the heating system, test resistance, and voltage, and verify that no connections are loose. A new ignitor will be required if the old one has given out. It is also possible that other parts of the furnace, such as the control board that supplies power to the ignitor, are malfunctioning and need repair or replacement.

2. Clogged or Dirty Furnace Filter

The proper functioning of a furnace depends on effective airflow. The return ducts allow the furnace to draw in cool air, which it then uses to heat and distribute throughout the house. The air filter plays an important role in this process because it captures dust, pollen, and other airborne particles.

This keeps them out of the furnace and out of your home. Nevertheless, as time passes, you can be faced with the issue of a dirty air filter which has the potential to accumulate debris and severely limit the airflow.

Several issues can arise when airflow is limited:

  • There may not be adequate air circulation in the system, leading to the furnace overheating and turning off too soon.

  • Overheating and possible furnace damage can occur when the heat exchanger is unable to dissipate heat as intended due to restricted airflow.

  • Worst of all, even if the burners do light up with little airflow, they may not burn the gas all the way through, which might cause a deadly buildup of carbon monoxide.

During the frigid winter months, when furnace consumption is at its highest, homeowners should inspect the filters more frequently. Depending on the filter type and how often you use your HVAC system, most experts advise changing the disposable filter every one to three months. You might have to change the filters more often if your home has pets or a lot of dust.

3. Gas Supply Issues

For a gas furnace to work properly, a steady flow of natural gas is required. The furnace will not light if the gas line is not working properly.

Problems with the gas supply often include:

  • The gas valve on the furnace itself can be mistakenly switched off from time to time, especially during installation or maintenance. Make sure this valve is completely open at all times.

  • There are a number of potential causes of interruptions to your home’s gas supply, including construction-related line damage and utility outages. It could be a sign of a larger supply problem if other gas appliances in your house are also not functioning.

  • Failed Regulators: You may adjust the gas pressure and flow into your furnace with the gas pressure regulator. In the event of its failure, the gas supply can be either completely cut off or reduced to an ignition-inhibiting level.

It is important to have experts handle gas supply concerns due to the potential dangers involved. It is critical to promptly vacate the area and contact emergency services and your gas company if you detect the smell of sulfur or rotten eggs, which could indicate a gas leak.

A licensed HVAC specialist can diagnose gas supply problems by checking the pressure and making sure all the fittings and valves are in good working order.

4. Broken Flame Sensor

When the gas valve is open, the flame sensor checks to see if a flame is present; otherwise, the gas could build up unburned and pose a danger. Soot and filth can prevent the flame sensor from detecting flames, which means the furnace will turn off soon after starting as a safety measure.

Taking the flame sensor apart and giving it a careful cleaning with steel wool or a fine abrasive pad is a delicate task. Without harming the sensor, this eliminates the accumulation. But you’ll have to get a new one if the sensor breaks or cracks. Despite its low price tag, this part is vital to the furnace’s safety and must work as intended.

5. Blocked or Leaky Gas Line

The gas lines carry the gas to the furnace, but they can get clogged or even burst at times. Debris that gets into the line during installation or maintenance, or a crack or squeeze that limits gas flow, are common reasons for blockages. Damage to the line, corrosion, or a lack of a secure connection can all lead to a leak.

Since working with gas is inherently dangerous, only a trained HVAC expert should be tasked with locating and fixing gas line obstructions or leaks. To find leaks, measure gas flow, and verifying the integrity of all connections, technicians will employ specialist equipment. Gas can travel through pipes and appear long after a leak has occurred, making it important to look for gas elsewhere in the house if you suspect a gas leak.


If you are facing the issue of a malfunctioning furnace where it fails to ignite, addressing these issues promptly is often necessary and must not be avoided. However, due to the technical and safety concerns involved, especially with gas furnaces and electrical components, it is advisable to seek the expertise of a professional HVAC service provider like Comfort Union.

Our skilled technicians can provide thorough diagnostics, effective furnace repairs, and regular maintenance to ensure your furnace ignites correctly, maintaining the comfort and safety of your home. Remember, timely intervention by experts like Comfort Union can prevent minor issues from becoming major problems.

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