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Carrier Furnace Not Igniting? 4 Common Causes

Carrier’s top-quality furnaces can keep your home warm during winter. But if your Carrier furnace isn’t igniting, you won’t get any hot air, making your home rather uninviting. There are a few common reasons that can cause this, often linked to a simple fix. 

Your Carrier furnace isn’t igniting because your gas valve isn’t opening, you have a clogged air filter, gas supply issues, or a dirty flame sensor. To fix the problem, inspect your gas supply to ensure there’s nothing wrong with it and clean or replace your air filter and flame sensor.

With the information provided in this article, you can determine why your Carrier furnace doesn’t ignite when you turn it on. Read on to learn how to identify and fix each issue.

Gas Valve Not Opening

When trying to determine why your Carrier furnace isn’t igniting, consider all options. Look out for signs of other underlying issues. If you hear a constant clicking noise, but there is no ignition, inspect the gas valve. 

This valve is inside the furnace. The gas supply line connects to the gas valve. The valve remains closed when the furnace is off. When you switch the device on, a signal tells the valve to open up and allow gas to flow into the furnace. The ignitor ignites the gas, and the burners sustain the flames to keep your home warm.

A few possible reasons can cause a gas valve not to open up. The first possibility is that the switch on the gas valve isn’t closed. If this happens, the gas valve won’t open up when the flame sensor calls for gas. 

It’s also possible that an obstruction is blocking the gas valve. The obstruction can cause the valve to get stuck when it opens. It could also block gas from coming out of the valve. 

How To Fix

You need to open up the furnace’s main compartment for this fix. Here’s what you have to do:

  1. Turn off the furnace.
  2. Open the panel to gain access to the main compartment.
  3. Check the switch on the gas valve. If closed, open it. 
  4. Return the panel, turn on the furnace, and see if the issue is resolved. 
  5. See if there are obstacles in the way of the gas valve. 

If the gas valve is damaged, watch this video to replace it:

Clogged Air Filter

When your Carrier furnace isn’t igniting, you first want to check the valves and gas line. While these are the common culprits, there may be a good reason why the gas valve is closed. Carrier furnaces have a safety switch that turns the furnace off if a hazard is detected. 

The accumulation of air inside the furnace’s main compartment is one of those hazards. This problem happens when the air filter is too dirty to allow proper airflow. 

Moreover, you need to replace the furnace filter every 30–90 days, depending on the type. If your furnace is fitted with a reusable filter, you still need to clean it frequently. 

You may have noticed that your furnace isn’t heating as well as it used to if the filter is dirty. That’s because there’s little air flowing through the filter due to all the dust and debris stuck inside of it.

How To Fix

How you go about fixing the issue depends on the type of filter used in your furnace. The first step is to determine whether your furnace uses a reusable or disposable filter:

  • If it’s a disposable filter, replace it. Instead of cleaning it, you need to buy a new one. Make sure you have the model number of your furnace with you. Carrier furnaces use different types of filters. 
  • If it’s a reusable filter, take it and clean it. Make sure you get all debris off the filter. If there are cracks or other signs of damage, consider replacing it instead. 

If you haven’t cleaned a furnace filter before, the video below can help:

Gas Supply Issues

Another area you should examine is the gas supply. If your Carrier furnace uses a gas tank, check if it’s empty.

It could also be that the gas canister’s valve is turned off. Note that this isn’t the same valve as the furnace gas valve. There’s a gas valve on each end of the supply pipe. If the gas valve is closed, you won’t get any gas.

How To Fix

To fix the issue, you need to determine what’s causing the gas supply problem. Here’s what you have to do:

  1. Check the pressure meter on your gas tank. See if there’s still gas left in the tank. If the pressure is low or there is no reading, you need to get a refill. 
  2. If there’s gas in the tank, check the valve on top or side of the tank. It’ll be next to the supply pipe.

Dirty Flame Sensor

You also want to ensure the flame sensor isn’t faulty or dirty. The flame sensor is responsible for checking whether there’s a flame in the system. If it cannot detect flames, it can cause problems with the rest of your system. This includes a failure to get the ignitor to create a flame. 

In most cases, it’s just some debris and soot on the flame sensor. But it could also be that the flame sensor is damaged.

How To Fix

Here’s how to fix the flame sensor:

  1. Cut all power to the furnace.
  2. Open the combustion chamber.
  3. Remove the flame sensor.
  4. Use fine sandpaper to clean the flame sensor. Don’t press too hard to avoid scratching it. 
  5. Inspect the flame sensor up close to see if it’s cracked. If you find a crack, buy a replacement sensor. 

Here’s a guide that shows you how to replace the flame sensor:


Your Carrier furnace isn’t igniting due to a dirty flame sensor or issues with the gas supply. A blocked air filter may cause problems with the ignition process as well. Ensure everything is clean and that the gas supply runs uninterrupted to the furnace, and your furnace should ignite again.


  • Vincent Steele

    Vincent is a freelance writer based in Santa Ana, California. When he isn't writing articles for Temperature Master, he can be found biking or hanging out with his cat, Shelly.

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