How to Test Furnace Ignitor With Multimeter

Furnace ignitors are small, heat-producing devices that ignite gas or oil burners at the beginning of a furnace cycle. Testing furnace ignitors with a multimeter is easy to diagnose problems and ensure your home stays warm all season. Testing furnace ignitors with a multimeter is a relatively easy and inexpensive way to diagnose problems.

How to Test Furnace Ignitor With Multimeter

A multimeter allows you to test the current flowing through your ignitor and compare it to manufacturer specifications. If you determine an issue with the current amount, you can pinpoint the source of your problem instead of just guessing what could be wrong. You can find step-by-step instructions on how to test furnace ignitor with multimeter in this blog article.

Step-by-step Instructions for How to Test Furnace Ignitor With Multimeter

Step 1: Inspect the Ignitor

Before you begin, carefully inspect the furnace ignitor. If there is any visible physical damage to the part, it should be replaced before testing with a multimeter. Ensure all electrical power to the furnace is shut off before beginning testing. You can do this by switching off the breaker switch located in the circuit box.

Step 2: Set the Multimeter to Ohms

Set your multimeter to measure ohms, normally indicated by an omega sign (Ω). This setting will allow you to measure resistance levels accurately. Identify where the two ignitor connections are located. Some furnace models may have just one connection, while others may have two.

Step 3: Connect Multimeter Leads

Attach the multimeter leads to the appropriate connections on the ignitor. Ensure you do not accidentally touch wiring or create a short circuit during this process. Check the meter readings for any values off the expected resistance levels. If there is an issue, it will normally be indicated by a low or high reading compared to a known good ignitor.

Attach the Multimeter Leads to the Appropriate Connections

Step 4: Check for Fluctuations in Resistance Readings

If you notice any fluctuations in resistance values while taking measurements, this could indicate a faulty ignitor connection. Once you have completed your tests, document the readings if further troubleshooting is required.

Step 5: Replace Faulty Parts

If any of the resistance readings or connections appear to be off or damaged, it may be time to replace the ignitor. Consult your furnace manual or a qualified technician for assistance. 

Once you have finished testing and replacing any faulty parts, switch the power back on and check that the furnace is functioning properly. It’s important to never work on a live electrical circuit, so make sure all power is off before beginning any work.

Knowing how to test your furnace ignitor properly will ensure your system runs efficiently with minimal downtime. With these steps in mind, you can easily check for potential issues and keep your furnace operating safely and reliably.

Common Causes of Testing Furnace Ignitors with Multimeter

  • Poor Connections: Faulty electrical connections can cause low resistance readings, as well as intermittent fluctuations in readings.
  • Worn-Out Ignitor: A worn-out ignitor will not produce enough current to ignite the burner and should be replaced.
  • Cracked Ceramic Core: If the ceramic core of an ignitor is cracked, it may lead to poor performance and should be replaced.
  • Faulty Wiring: Corrosion, broken wires, or loose connections can all impact an ignitor’s performance.
  • Damaged Components: If any components, such as a resistor or capacitor, are damaged, they may cause low resistance readings and should be replaced.
  • Overheating: Overheating is a common cause of ignitor failure and may result in high resistance readings. Make sure to give your furnace time to cool before taking measurements.
Faulty Electrical Connections Can Cause Low Resistance

Testing your furnace ignitor with a multimeter is an easy way to diagnose potential issues and ensure that your home stays warm all season. Be sure to take the necessary safety precautions, such as switching off the power, before beginning work.

Safety Tips for How to Test Furnace Ignitor With Multimeter

  1. Always wear eye protection and gloves when testing a furnace ignitor with a multimeter.
  2. Turning off the power to the furnace before beginning any testing is important.
  3. Ensure you read the user manual that came with your multimeter for instructions on using it correctly.
  4. Check the ground connection of the circuit breaker or fuse panel and the power cord of the furnace before you start testing.
  5. If possible, use a thermometer to test the temperature of the ignitor fuse and its connecting wires. This will help determine if there is abnormal heat in those areas.
  6. Test all settings on your multimeter, such as current, voltage, continuity, and resistance.
  7. Check the wiring between the furnace and the ignitor to ensure no damage may cause a faulty reading.

By following these safety tips, you can save time and money by testing your furnace ignitor with a multimeter correctly and safely. It’s important to remember that it is always best to consult an HVAC technician if you need clarification.

What Steps Should You Take to Test the Furnace Ignitor With a Multimeter Properly?

  • Begin by connecting your multimeter probes to the appropriate ports in the furnace ignitor. Then, turn the power to the furnace and ensure it runs correctly.
  • Set the multimeter to “resistance” mode and check its reading. If there is no resistance, you know something is wrong with the ignitor.
  • Change the multimeter to “voltage” mode and recheck its reading. If the voltage is too low, you know there is a problem with the wiring or connections of the furnace ignitor.
  • Check for continuity by setting your multimeter to “continuity” mode and ensuring a current is running through the ignitor.
  • Test for any potential shorts by setting your multimeter to “current” mode and checking for any unexpected drops in amperage.
  • If all of these tests turn out normal, you know your furnace ignitor is working correctly, and no further action needs to be taken.

Following these steps, you can properly and safely test your furnace ignitor with a multimeter and ensure it functions correctly. If anything appears wrong or you need clarification on the process, it is always best to consult an HVAC technician for further assistance.

Where Can You Find More Information About Testing Furnace Ignitor With a Multimeter?

If you need more information about testing a furnace ignitor with a multimeter, plenty of resources are available. You can start by checking out your local home improvement store. They should have a selection of books and guides that will provide detailed instructions on how to test the ignitor with a multimeter. Online forums such as DIY Network or HVAC Talk can also offer advice from experienced professionals.

Additionally, contact the manufacturer of your furnace or ignitor unit. They will have specific information on testing the device and ensuring it works properly. If you already have a multimeter, they can provide more detailed instructions on using it with your particular furnace ignitor.

Finally, you should always ensure you wear the proper safety equipment when testing a furnace ignitor with a multimeter. Safety glasses and gloves are always recommended to protect yourself from any potential electrical hazards.

Wear the Proper Safety Equipment

What Are the Most Common Mistakes to Avoid When Using a Multimeter for Furnace Ignitor Testing?

When testing furnace ignitors using a multimeter, it is important to take certain precautions to ensure your and your home’s safety. Here are some of the most common mistakes to avoid:

  • I am not double-checking all connections before proceeding with the test. Ensure all wires are securely connected, and no bare wiring is exposed.
  • It needs to be ensured that the device is completely disconnected from power sources before proceeding. It is important to disconnect the hot and neutral wires from the energy source before starting any testing.
  • Not using appropriate insulation when handling live wiring can cause accidental shocks or other dangerous outcomes.
  • They were not wearing protective clothing such as gloves and goggles when handling the multimeter.
  • Double-checking them with a calculator or another measuring device only ensures that some readings are accurate.
  • Being familiar with your multimeter’s specific settings can lead to correct readings and false results.
  • They are testing only a few times to ensure that results remain consistent.

By taking these simple precautions, you can ensure that your furnace ignitor test is done safely and accurately. Additionally, if you need help with the testing process, it is always recommended to contact a professional for assistance.

Are There Any Special Maintenance Requirements for the Furnace Ignitor After It Has Been Tested?

Once the furnace ignitor has been tested with a multimeter, it is important to check for any signs of damage. If the ignitor shows any signs of wear and tear or loose wires, it should be replaced immediately. Additionally, periodic maintenance checks are recommended to ensure that the ignitor is functioning properly and not in danger of failing.

Furnace Ignitor Has Been Tested With a Multimeter

To ensure optimal performance, it is essential to check that all connections are secure and that the ignitor coils are debris-free. Finally, never store a furnace ignitor in a damp or humid environment, which can lead to corrosion and permanent damage. With proper testing procedures and regular maintenance, your furnace ignitor should provide years of reliable operation.


In conclusion, testing a furnace ignitor with a multimeter is an easy task that can save you time, money, and frustration. By following the steps outlined in this article, you can quickly determine whether your furnace ignitor needs to be replaced.

It’s important to remember that although testing a furnace ignitor with a multimeter requires some knowledge about electricity, it’s a relatively simple process that anyone can do. I hope reading this post has helped you learn how to test furnace ignitor with multimeter. Make sure the safety precautions are carried out in the order listed.

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Enrique Howard

Hi, I am Enrique. I started my professional life as a handyman and did a lot of external and internal repair of home and office with a little bit of electric and plumbing support. I have extensive experience in tools testing such as drilling, turning, milling, and non-conventional machining like EDM. So let me help you on your journey towards becoming an enlightened DIYer with amazing tools that you can use on your project.

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