Furnace Not Igniting – How to Check and Replace Ignitor (Step By Step Guide)

So your furnace is not heating and you think that your ignitors have gone bad. A simple visit from a technician can cost a minimum of $200 in case of ignitors. 

I have been in the HVAC repair business for about 6 years now and I know that this is not a major problem and can be solved by yourself at home.

So In this article, I’ll tell you how you can troubleshoot and test your ignitor at home. And how you can replace them. Remember that ignitors are not that expensive they usually cost between $30- $60. So you don’t have to stress over it and also the installation of a new one is pretty easy.

Different Types of Ignitor’s

First, let’s discuss different types of ignitors:

Standing Pilot Ignitors: Only very old furnaces have those. These types of ignitors have to manually light the flame and that little flame stays on all the time.

And if you think you have that but you’re not sure an easy way to check is to just look on your gas valve and usually it’ll have a knob on top of it that’ll have an on, off, and a pilot position.

Direct Spark Ignitor: These are generally pretty loud ignitors. If that’s what you have you’ll probably hear it when the furnace is trying to start it’ll make a pretty loud racket.

So with a direct spark igniter, the gas valve opens and sends gas through the manifold to all the burners and that spark ignites the gas right away.

Intermittent Pilot Ignitors: So it’s kind of like a standing pilot but it’s intermittent. So it only turns on when there’s a call for heat when the thermostat is calling for heating.

So you have a little pilot hood and usually, the gas valve will have a little silver tube coming out of it that’ll be the pilot tube.

So whenever there’s a call for heat the pilot valve opens on the gas valve and lets a little bit of gas through and then a spark will ignite that pilot flame and once a flame sensor or a thermocouple senses that the flame is there. Then the main gas valve opens up and lets the flame through.

Hot surface ignitor: They use a little glow stick that glows up to about 1200 degrees and that’s what ignites the gas. Most of the furnaces have this one ignitor installed.

How to Troubleshoot Your Furnace Ignitor?

Step 1: Turn Your Furnace Power Off and Remove the Furnace Door

furnace switch

The first thing you should do is turn your furnace switch off. And then remove the doors of the furnace. 

Step 2: Now Turn Your Furnace Switch On and See What the ignitor does.

Now the second thing you need to do is turn on the furnace switch again. 

After this, you’ll see your inducer motor getting started. Then you’ll hear your gas valve open up (usually a click sound). If the gas started to flow but nothing is happening (not igniting) then your ignitor is bad.

Step 3: Check Your Ignitor Switch 

Now if your ignitor is not working then you can try to check your ignitor switch. Sometimes that switch becomes loose and that’s what causing the ignitor to not work. Tighten the switch and check if your ignitor starts glowing or not. If it doesn’t glow then your ignitor is bad and you need to replace it.

Step 4: Check Your Ignitor With Multimeter

With a multimeter, you can check the ignitor’s voltage and resistance. Both the inspection are necessary so do test for both things. 

Checking Ignitor’s Voltage 

If the ignitor is getting voltage but it’s not igniting that means the igniter is bad. But if it’s not getting voltage that means something else is wrong or maybe the control board is bad and it’s not sending power to it. 

So to check the ignitor’s voltage Just remove the ignitor switch and put your multimeter leads into the switch and check how much voltage it’s getting. It should be around 120 +-Volts. If the meter is not showing anything or too low voltage then there’s something else. Your ignitor switch is not getting current from the control board and you need to check it.

How to check Your Ignitor with a multimeter?

Now once you checked the voltage if it’s getting proper voltage. Then you need to check your ignitor’s switch with a multimeter. 

Now set your multimeter to ohms and put the leads into the ignitor’s switch. The ideal ohms rating for a good ignitor is between 40-90.

So if your ignitor’s rating falls between that limit then your ignitor is good. And if it’s jumping to 100 or 250 then it’s close to its end cycle. One thing to note is that you should always check your ignitor’s resistance at room temperature. Because if you take a working furnace ignitor reading (resistance) then the results may vary.   

How to replace your Furnace Ignitor?

Step 1: Turn Your Furnace Power OFF

furnace switch

The first thing you should do is turn your power switch off. Because you don’t want to operate furnace while the power is running. It can be fatal if you do that.

Step 2: Remove Your Switch and Unscrew Your Ignitor

Now you need to unplug the ignitor’s switch and unscrew the ignitor. 

Step 3: Replace the ignitor and put it back

Now you need to replace the ignitor with a new one. To do that just unscrew the ignitor’s bracket and remove the old one and replace it with the new one. Now put your ignitor back on the furnace and plug the switch back and check if it’s working properly or not.

Also, Check Out Our Furnace Repair Guide: 11 Most Reported Furnace Problems With DIY Solution

Scroll to Top