Furnace Not Igniting: What Are Common Causes & How To Fix

The idea of having a malfunctioning furnace in the coldest winter months sends shivers down any spine... not quite as chilling as when the furnace fails to heat up.

If your gas furnace ignitor is not working, you can have either a minor inconvenience or major problem if outdoor temperatures are freezing. Electronic ignition system problems tend to cause gas furnaces to shut down or even long-term system outages.

In this guide, we’ll help you diagnose the cause to this common furnace issue and help you determine what you can check before having to call for emergency heating repair service.

Why Is My Furnace Not Igniting?

If your furnace is not kicking on, any number of problems could be the culprit. Each furnace has its own internal components that will need to be inspected in order for this problem to be resolved. A furnace converts heat energy from gas to warm up the air and distribute it throughout your home or building.

If you smell gas, leave your house immediately and call 911. If you see a blinking light on your furnace, contact a furnace repair company immediately.. If you don't smell gas, or see any flashing lights, check each of these items to determine the cause of your ignition issue.

Gas Line Issue

One of the most common reasons a furnace is not lighting is when your gas line is blocked or clogged. The line in which the furnace draws its fuel can be either blocked or too small for the furnace. If this gas valve or gas supply is obstructed in any way, your furnace will not be able to get enough natural gas to start up correctly and safely, leaving you with no warmth inside your home.

The solution here would be to get a technician to come check out your system. An expert can check where your furnace’s source of natural gas comes from and if there are any city gas line obstructions such as tree branches or debris blocking it. Ideally, you should have at least six inches of clearance for this line to function properly.

If your furnace requires a larger gas line than what you’re currently using, you’ll run into problems with your furnace not igniting. This can be confirmed with a gas pressure gauge, which our technicians have and know how to use. Our techs can contact the manufacturer of your furnace and purchase an adapter that will allow you to connect a larger gas line.

You’ll need to make sure you don’t run the risk of having too much gas flow through your furnace because it could damage internal parts like the pressure regulator or safety controls. Having too little gas, however, is easily remedied by adding on additional length of natural gas piping or an adjustable regulator.

Malfunctioning Thermostat

You may be experiencing issues with your furnace either not turning on or simply not producing any heat. These problems could be easily remedied by either replacing your furnace’s thermostat or calling a technician to come inspect it, as there might be other issues contributing to the furnace not igniting.

If nothing seems to be working on your furnace even after you replace its components, a furnace replacement may be in your near future. This is a better choice than constantly investing in new parts that won’t work.

Dirty Furnace Filter

Your furnace’s air filters should be changed anywhere from every 90 days up to four times a year if they're experiencing some major furnace problems. A dirty air filter makes cleaning out any debris before it can cause problems later essentially impossible. That’s because it clogs itself over time with dirt and dust particles that reduce the going into your furnace.

The simplest furnace fix you can do for this issue is to change your air filter. Call a furnace repair technician if the problem persists.

Defective Igniter or Pilot Light

If your furnace has been working without any problems up to now and suddenly will not ignite, there’s a good chance that either the electronic ignition system has failed or that the standing pilot lights that comes before the ignition process has gone out.

The first step here would be to determine which of these two components isn’t working by paying attention to what your furnace does before it tries igniting again. If it makes a clicking noise but your furnace won’t ignite after its combustion cycle, then it’s more than likely going to need to replace the electronic ignition systems.

In cases where furnace ignition starts up normally but only fires for a couple minutes and shuts off, it’s most likely going to need a new standing pilot light installed.

Dirty Gas Burners

Dirt accumulates on the burners of your HVAC system, preventing them from burning evenly and at the proper height. The thermostat is set to a temperature lower than the target, which causes your heating system to work harder and consume more energy in order for your home to be warm. The flames may not completely burn when the burners are clogged with debris, creating a higher amount of carbon monoxide in your system.

You can clean them in place by blowing compressed air through each of them and wiping the outside with a brush or rag. It also helps to dust your house on a regular basis to keep dirt out of your furnace.

Broken Flame Sensor

Another furnace issue is when their furnace won’t stay lit because the flame sensor isn’t working properly. A furnace’s flame sensor determines if it should continue firing off and will shut down if necessary once it detects a faulty flame signal. This furnace error essentially creates an out-of-control furnace that doesn’t know when to stop producing high amounts of heat, which can lead to overheating in your furnace and cause parts to burn out prematurely.

To remedy this, you’ll need to clean the air vents for your furnace and then unplug it until a service technician can come take a look at what might be wrong with the furnace and fix its various components.

Strong Draft

If there is a strong draft in your basement or attic, or if you are experiencing high winds, the pilot light may not light. In addition, if your furnace has a draft motor or blower that is malfunctioning or dead, the pilot won’t light.

The purpose of the draft motor is to pull air into and out of your chimney or vent. The motor, like other furnace components, may go bad with time.

Additionally, blocked chimneys or furnaces can prevent the engine from drawing in air. As a result, the igniter will not light. You should hear a faint hum when the draft motor is in good order. If there is a blockage, you may hear a muffled hum as well as burning fumes.

Should I Replace My Furnace If My Ignitor Stops Working?

It is common for an ignitor to go bad in most furnace types. This can be very frustrating because this may require furnace repair technicians to come out and fix, which could cost you. It depends on the age of your furnace and how frequently you’ve had to make furnace repairs to determine whether a new furnace installation is in order.

There is no definitive answer, of course, but a reasonable general estimate is about 10 years, depending on regular maintenance and usage history. Once it’s been decided that repair isn’t an option, you should find out everything there is to know about all of your choices, the benefits and drawbacks of each, and most importantly that your new heating system is installed by experts who are trained.

Fix Your Electronic Furnace Ignition With ARS/Rescue Rooter

HVAC technicians at ARS/Rescue Rooter can identify heating issues and damage to your heating system, as well as replace heating components as needed to restore heat function. Call ARS/Rescue Rooter now to schedule an appointment with a local heater repair expert for furnace repair service in your area! We service units from Lennox, Carrier, York, and other popular brands.

Common Furnace Ignition Questions

My gas furnace won’t ignite. What should I check first?

Checking your thermostat is the best place to start. Make sure it’s set to “heat” and that you’ve set the temperature higher than the current room temperature. If that doesn’t resolve the problem, try switching your fan to “on” to force the furnace to start working. Look to see if your thermostat is showing any error codes. If these steps don’t solve the issue, there may be something more complex at fault.

How can I determine if there’s a gas-related issue causing my furnace problem?

You can start by checking to see if your gas supply is turned on, which is usually controlled by an exterior shut-off valve. You could also try testing another gas appliance in your house, such as the stove. If the gas supply seems fine in other appliances, check the supply line for your furnace. If the line is disrupted, your furnace may not have enough fuel to ignite. If you smell gas or believe there might be a gas leak, leave your house and call 911 ASAP.

My furnace is not turning on. Could blocked air ducts be the issue?

Obstructed air ducts can hurt your furnace’s performance. Look for any gaps in the ductwork and seal them with metal tape. If you have heat in some rooms but not others, this could be the problem. You also should replace or clean your air filters to ensure proper airflow. Also, consider having a professional duct cleaning service clean out your air ducts to ensure efficient performance.