Skip to Content

Furnace Ignitor Not Getting Hot Enough? Here’s What To Do

The ignitor in your gas furnace has a crucial role — when you switch on the furnace, the ignitor heats up and ignites the gas. However, sometimes the ignitor doesn’t get hot enough, leaving your house colder than it should be.

A furnace ignitor not getting hot enough can happen because it’s dirty, the thermostat is broken, there’s a missing connection between the two, or the ignitor is damaged. Fix the ignitor by cleaning or replacing it, repairing or replacing your thermostat, and fixing the wiring.

This article will give you an overview of common reasons why your furnace ignitor isn’t getting hot enough. I’ll also share the appropriate solutions to help you gain back control over your indoor temperature.

The Ignitor Is Dirty

One of the most common reasons for furnaces to become faulty is due to the collection of debris. Many people think that the furnace’s filter will catch all dust. 

But what about the dust and particles that are pushed into the system before reaching the filter?

Studies show that different cleaning methods can effectively improve the functionality of the HVAC system. This includes cleaning methods used on the ignitor — the one part of the furnace essential for ensuring air is heated up. 

How To Fix

You need to remove the furnace cover. Some furnaces come with a door at the front. Others have a fastened cover. 

Use the appropriate method to ensure you can get inside — you want to focus on reaching the ignitor.

The exact steps vary depending on the type of furnace you have. Check the user manual or have a professionald do it if you’re not sure. Either way, here are a few tips that’ll help you clean the ignitor:

  • Don’t use chemicals on the ignitor. Chemicals could cause problems with your ignitor. If a flammable chemical is used, there’s a good chance it’ll create large flames in the furnace. It can be a major fire hazard for your family.
  • A can of pressurized air is an excellent option for cleaning the ignitor. The nozzle will allow you to blow dirt out of small holes. 
  • Use a small brush to reach tight spaces in the ignitor. If pressurized air isn’t enough to remove debris that has accumulated, a brush will take care of the rest.

The Thermostat Isn’t Working Correctly

The furnace uses a thermostat to regulate temperature. You can adjust settings on the thermostat, which consequently affect the ignitor and the furnace. A higher temperature on the thermostat means more gas passes to the ignitor. This results in a hot ignitor and a larger flame.

When the thermostat has problems, it can cause problems with the ignitor too. 

However, changing the settings on a faulty thermostat won’t result in appropriate gas pressure adjustments or the intensity of flames in the ignitor. 

So, you’ll need to test the thermostat independently.

How To Fix

You first need to test the thermostat to see if it’s faulty.

If you have a spare thermostat, use it. Connect the spare thermostat to the furnace and see if it affects the temperature of the ignitor.

You can also try to reduce the temperature on the thermostat — just for testing purposes. See if this affects the ignitor at all. If the ignitor gets colder, the problem lies elsewhere. 

When the thermostat is the fault behind your furnace ignitor not getting hot enough, you need to fix or replace it. 

Determine what the problem is, then see if the issue can be fixed. If there’s no easy way to fix it, replace it.

Looking for a visual overview to help you troubleshoot the thermostat? Watch this video:

There’s a Missing Connection Between Thermostat and Ignitor

As mentioned already, the thermostat plays an important role in regulating your home’s temperature. When the thermostat doesn’t affect the ignitor’s temperature, it’s not always the thermostat itself that is faulty. 

Sometimes, it’s something as simple as a loose or missing wire between the thermostat and ignitor. 

It could also be that the wire is damaged or broken.

How To Fix

Fixes for a problematic connection between the ignitor and thermostat often turn out to be quite simple. You should, however, be cautious during this diagnostic step. 

Here’s how to fix faulty wiring:

  1. Turn the furnace off.
  2. Remove the front panel on your thermostat.
  3. Inspect the wire that connects the ignitor and the thermostat. Check the whole wire from start to finish, not just the ends.
  4. If the wire is disconnected but otherwise in good shape, put it back in.
  5. If the wire is damaged anywhere, replace it.

The Ignitor Is Damaged

The ignitor wears out over time. Superficial cracks can make a bigger impact than you think. Thus, you need to know when to replace the ignitor.

Note that damage to the ignitor typically won’t cause the furnace to cease functioning. It could simply reduce the efficiency of the ignitor, leading to reduced heat generation. 

How To Fix

If your ignitor is damaged, you need to remove it from the furnace. Once removed, you need to buy a new one. Compatibility is important, so double-check the type of ignitor your furnace uses. 

Fortunately, this process is often not too complicated. You’ll only need a couple of tools.

Here’s a video showing you how to replace a furnace ignitor:

If you’re not experienced, you can end up damaging the furnace or even the new ignitor.

There are also additional risks involved when working with the electronic components of the furnace. Always consider your own safety when trying to fix a problem. After all, you’ll have to open up the furnace box and work on the inside.

Calling a professional to fix your furnace is a more effective option. The expert will diagnose what’s wrong with your ignitor and fix or replace it. This eliminates safety risks and ensures the furnace doesn’t get damaged. 


Your furnace ignitor won’t get hot enough if it’s dirty or broken. Cleaning or replacing your ignitor is often the best solution. However, you should also check if there are problems with the thermostat and the wiring beforehand. It may be something as simple as a loose wire that needs to be reconnected.


  • Steve Rajeckas

    Steve Rajeckas is an HVAC hobbyist with an avid interest in learning innovative ways to keep rooms, buildings, and everything else at the optimal temperature. When he's not working on new posts for Temperature Master, he can be found reading books or exploring the outdoors.

As an Amazon Associate, we earn from qualifying purchases. We may also earn commissions if you purchase products from other retailers after clicking on a link from our site.