If your furnace won’t ignite, the source of the issue may be a broken flame sensor. The sensor is responsible for turning off the gas burners to avoid gas buildup. Once this component starts to malfunction, it may stop the burners from igniting altogether.

Why is my furnace running but not igniting?

If your gas furnace initiates the start cycle but does not fire up, it’s likely because of a faulty, damaged, or dirty ignitor/sensor. This is a very common furnace problem—you can try to clean the sensor and replace the ignitor.

How do I know if my furnace ignitor is bad?

If you have a faulty furnace ignitor, it won’t produce that tiny spark to heat the air coming from your Furnace. Your heater blows air at the same temperature as the cold outside air without it. Cold air blowing through your vents is a good sign that you have a heating problem within the Furnace.

How do I get my furnace to ignite?


  1. Look for a switch inside or near the furnace that turns it on and off. Make sure that it’s set to on.
  2. Make sure the gas valve is turned on.
  3. Examine the circuit breaker for the furnace. …
  4. Check the pilot light. …
  5. Leave the setting for lighting the pilot on for a few minutes after getting it lit.

How do I reset my furnace ignitor?

Once the power is off you can remove the burner door to reveal the ignitor. Turn this to “off” and leave it off for at least 5 minutes. After this time, turn the ignitor back to the “on” position and replace the burner door. You can then turn the power source back on and restart the furnace.

How much does it cost to replace an igniter on a furnace?

Here’s the bottom line: Whether for a natural gas furnace, oil, or a propane furnace, replacing a furnace ignitor–including parts and labor–will cost you around $300 – $425 for a qualified contractor to install. Compare that to, say, a draft inducer motor, which will cost $400 – $1,500 to replace.

Can I clean a furnace ignitor?

If your furnace has a spark ignitor and it’s working haphazardly, it too could be covered with soot, and a blast of compressed air may be enough to clean it. Compressed air can also clean a blocked pilot tube that is causing the pilot flame to burn weakly or not at all.

How do you manually ignite a furnace?

Once the gas has had time to dissipate, turn the knob to “Pilot.” Then, hold down the “Reset” button and bring the flame of a long lighter close to the pilot light opening. This should light the furnace pilot light. Once you are sure the pilot light is on, release your pressure on the reset button.

Is it safe to manually light a gas furnace?

Never attempt to light a furnace by a flame manually, especially if the furnace has an electronic igniter. A furnace equipped with an electronic igniter cannot be lit manually. Call for the services of a professional heating and cooling technician when the igniter is not working properly.

Can I light my furnace with a lighter?

Turn the switch off, and wait at least five minutes to allow any remaining gas to dissipate. Next, turn the switch to “pilot,” and hold down the reset button. Use a long lighter to light the furnace pilot light. Once it’s got a flame, which can take about 30 seconds, you can release the reset button.

Where is the flame sensor in my furnace?

A furnace flame sensor is a very basic part of your furnace. It’s located on the burner assembly and is just a thin metallic rod. It’s usually bent, and it sits just in front of the pilot flame inside the furnace.

What does a flame sensor in a furnace look like?

It will look like a thin metallic rod and is set in front of the pilot flame on the interior of your furnace. Both of these parts can be located inside of the burner assembly of your furnace which is typically in the bottom of your furnace. Having a dirty flame sensor can result in your furnace not starting.

How often should a flame sensor be cleaned?

The service life of a furnace is 10 to 20 years on average. This means you’ll have to replace a flame sensor once, twice or three times over the course of the furnace’s life. Having a bad flame sensor is completely normal–you just need to know how to properly identify when it’s gone bad so you can replace it on time.