Your furnace requires a consistent supply of power to operate. When there’s a voltage drop, you may find that the furnace operates abnormally, and you’ll need to fix the voltage issue to get things running smoothly again.
If your furnace ignitor isn’t getting voltage, potential causes include loose or damaged wiring, faulty control board, opened switches, or a damaged ignition controller. Fixing the issue starts with a test on the main control boards and looks for wiring problems and opened switches.
This article will help you understand why the voltage that goes to your furnace ignitor may be limited or non-existent. I’ll walk you through the most common causes for a drop in voltage and explain the most effective solution for each potential scenario.
Loose or Damaged 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.
Faulty Control Board
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:
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.
Damaged Ignition Controller
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:
- The first step is to disconnect the controller from the ignitor.
- Once disconnected, you will need to see if there is any voltage reading on the ignition controller.
- 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.
- When a voltage of 115 to 120 can be read, the problem does not lie with the controller.
- 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.
The Easiest Fix
If you don’t have the time or expertise to diagnose and fix your furnace’s voltage problems, your best bet is to hire a furnace repair expert to do it for you.
Believe me, I know how hard it is to find a trustworthy and affordable repair service. Some never call you back. Others charge you sky-high rates. And the worst ones simply don’t know what they’re doing. Ugh!
To eliminate that frustration and bring you fast and affordable repairs, I’ve partnered with a company called Networx. They make it easy to get free quotes from trusted furnace repair services near you.
Here’s how it works:
- You fill out the form below. You just need to add some basic contact information and a brief description of your problem.
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- They’ll come to your house and fix your furnace voltage issue. Problem solved!
Fill out the form now to get free quotes from trusted repair services in your area!