Furnace Ignitor Not Getting Voltage? Here’s Why + What To Do


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The furnace requires a consistent supply of power to operate. These systems are essential for maintaining clean air quality indoors and for regulating temperature. When there is a voltage drop, you may find that the furnace operates abnormally. 

Fixing low voltage on a furnace ignitor starts with a test on the main control boards and looks for loose and damaged wires, checks for opened switches, and identifies the area where voltage is being lost. 

This article will help you understand why the voltage that goes to your furnace ignitor may be limited or non-existent. We consider common causes for a drop in voltage and present you with the most effective solution for each potential scenario. 

Check for Disconnected Wiring

People often jump to one of the more serious scenarios when they consider the reason behind a furnace ignitor not getting voltage. While there are times where a significant problem will be found, this is not always the case. 

Sometimes the fault is simple – and this makes it easy to fix. 

Wiring in the furnace allows power to be distributed throughout the entire system. Even just one loose wire could cause problems, resulting in power loss in the specific area. With this in mind, it is a good idea to start by looking at the wiring inside the furnace. Consider all areas of the furnace, including wiring that leads to the ignitor. 

How To Fix:

Fixing an issue with wiring depends on the specific problem. Wires may be disconnected, or they could be damaged. The solution with these two problems is different – so you will need to remove the furnace cover and look at the wires on the inside:

  • You will need to rewire any disconnected cables inside the furnace. This includes wires that supply the ignitor with power. 
  • New wiring will be needed in areas where damage is found in existing cables. See if the entire cable can be replaced when you find damage. It’s usually not a good idea to try and fix damaged areas in a cable, as it may simply lead to more problems down the road. 

The Control Board May Be Faulty

Wiring is not the only element that helps to regulate the distribution of power in a furnace. The control board has an important role in providing power to each part of the furnace and HVAC system. This is why your second task should be to test the control board. 

A faulty control board can cause problems with the supply of power throughout the entire HVAC system. This particular problem can also make it hard to adjust the temperature and other functions to work properly. 

How To Fix

If you are going to test the control board, you will need to gain multimeter access. The multimeter will be used to ensure you get an accurate measurement of the board’s voltage reading. You may also need additional tools since you will open up the furnace to get to the control board:

  • Once you find the control board, place the multimeter’s nodes on the pins that are part of the board, and get a reading on each. Do this one at a time to ensure you can see if power drops at a specific point. 
  • Also, look for any abnormal “spots” on the board. If there was a power surge, for example, it could have damaged the control board. In such a case, you will sometimes see a burn mark on the board. 
  • Test the wires coming into the board and those going out to the ignitor. 

If the control board has been damaged, then you need to replace it. The process of replacing the control board is more complex compared to other solutions. 

For a visual demonstration of how the process works, take a look at this video: 

There Might Be Opened Switches

Numerous switches can be found throughout your furnace. These switches need to remain closed to ensure power can run through the furnace, toward the ignitor, blower, and other parts that make the system work. 

When there are opened switches in the system, then the power supply may be disrupted. This can cause insufficient voltage delivery toward specific parts of the HVAC system. Switches that run toward the region where the ignitor is found may affect this hardware’s power supply. 

How To Fix:

You will need to learn how you can test the switches used in the furnace’s power grid. Testing the switches will allow you to determine if they are opened or closed. When you find opened switches, there is a chance that these are contributing to the furnace ignitor not getting voltage. 

Take note that not all switches should necessarily be closed. The best configuration depends on your needs, the type of furnace you use, and your house setup.

To learn more about troubleshooting switches on your furnace, the video below might help.

The Ignition Controller May Be Damaged

There is more than one circuit board in a furnace. In addition to the primary board, take note that the ignitor also has its own controller. When this controller is damaged, the power supply to the ignitor may be cut off. 

A damaged ignition controller will often not be repairable. With this in mind, there is a good chance you need to find a replacement if this is your situation. Still, you first need to learn how to identify problems with the ignition switch and verify if this is where the voltage loss occurs. 

How To Fix:

A voltage meter is required to test the ignition controller. The process of testing the ignition controller is rather simple: 

  1. The first step is to disconnect the controller from the ignitor. 
  2. Once disconnected, you will need to see if there is any voltage reading on the ignition controller. 
  3. The ideal reading at the ignition controller should be between 115 VAC and 120 VAC. This is the reading you should see when the ignitor itself is not connected to the controller. 
  4. When a voltage of 115 to 120 can be read, the problem does not lie with the controller. 
  5. In case you get a 0 reading on the voltage meter, then it means the problem is with the ignition controller. You will need to get a replacement controller installed to fix the problem.

Here’s a video you might find useful if the problem lies with the ignition controller:

A voltage drop in the ignitor could mean wires are not correctly connected or can be a sign of control board damage. Use the tips we provided to help you understand the issue and identify the best way forward. 

A quick call to a local HVAC expert ensures your furnace and ignitor are fixed without delay or risks. These experts have years of experience, ensuring they can quickly determine why there is a lack of voltage in the ignitor and provide the solution needed to restore its functioning. 

Summary

Gas furnaces rely on an ignitor to ensure they can produce heat. There are numerous problems that an ignitor can face, with low or no voltage being supplied, potentially causing a cessation of heat provisioning. 

When it comes to finding the right HVAC specialist, you need to do your research and choose the option that fits your needs. The form below takes your location and requirements into account and gives you the ability to find a specialist to diagnose and fix the problem easily. 

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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