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 sparking, it can be a minor inconvenience or major problem if outdoor temperatures are freezing. Electronic ignition system problems tend to cause gas furnaces to shutdown 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 you have a furnace and it won't ignite, there could be any number of problems. Each furnace has its own internal components that will need to be inspected in order for this problem to be resolved. A furnace is essentially an appliance where heat energy is converted from the gas furnace to warm up the air and distribute that warmth throughout your home or building.

If you smell gas, leave your house immediately and call your gas company. If you see a blinking light on your furnace, it would be best to understand what error codes your systems is telling you too. 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 igniting is when the line in which the furnace draws its fuel is either blocked or too small for your needs. 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 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.

Another furnace issue that can arise is if your furnace requires a larger gas line than what you're currently using. This can be confirmed with a gas pressure gauge. The solution to this would be to 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

One common furnace problem people beginning to notice is when their furnace either will not turn on at or turns on but doesn't produce any heat. These problems could be easily remedied by either replacing your furnace's thermostat or call a technician to come inspect it, as there might be other issues at play behind the scenes.

If nothing seems to be working on your furnace even after you replace its components, it may be time for a furnace replacement rather than constantly investing in new parts that won't work.

Dirty Furnace Filter

Your furnace's air filters should be change 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 and 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 furnace issue is to change out your air filter and if this furnace problem persists, call a professional furnace repair technician.

Defective Igniter or Pilot Light

If you 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 fails or 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 people don't think about 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 big bucks. 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 guide might be 10-20 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!