How to Tell if Your Furnace Control Board Is Bad

A furnace control board, also known as a furnace motherboard or furnace circuit board, is the brain of your HVAC system that regulates and controls the functions of your furnace. Without it, your furnace won’t be able to work, leaving you in a cold and uncomfortable environment. However, like all electronic components, furnace control boards can fail over time, leading to a range of issues in your system. In this blog, we will explore how to tell if you have a bad furnace control board.

What Is the Furnace Control Board?

A furnace control board is an essential component of heating systems that regulates and controls the operation of the furnace. It provides instructions to the furnace’s various components, such as the igniter, blower motor, gas valve, and thermostat to generate and distribute heat within a home or building.

The control board uses advanced software and electronic circuitry to monitor the temperature, airflow, gas pressures, and other important parameters that affect the furnace’s performance. It processes the data received from these sensors and makes precise adjustments to ensure that the furnace runs efficiently, safely, and reliably.

One of the most crucial functions of a furnace control board is to manage the ignition process. When the thermostat detects the need for heat, the control board signals the igniter to begin heating up. Once the igniter reaches the appropriate temperature, the control board opens the gas valve, which allows the fuel to flow into the furnace’s burner tubes. The igniter then ignites the gas, and the furnace begins producing heat.

Besides managing the ignition process, the furnace control board also oversees fan control. It activates the blower motor when the burners are lit and turn it off when they go out. Through advanced algorithms, the control board ensures that the blower motor operates at optimal speeds to distribute warm air evenly throughout the home.

Do You Have a Bad Furnace Control Board?

A furnace control board can fail due to many reasons and require replacement. This system malfunction can produce a few signs you may observe with your furnace’s performance – if you notice signs of a bad furnace control board, it’s important to call us for furnace repairs right away.

If you notice that your furnace is not turning on at all, it could be due to a blown fuse or a tripped breaker. You can check the fuse or breaker to ensure it’s not the problem. However, if the issue persists after you check these issues, it could be a sign that the control board is bad.

If your furnace’s blower fan runs constantly, even when you’ve turned off the heat, this could indicate a bad furnace control board. The board signals the blower fan when to turn on and off, so an issue with the board can cause it to run all the time.

If your home is not heating evenly, with some rooms being warmer or colder than others, this could be due to a faulty control board. The board regulates system components that control the temperature and airflow throughout your home, so if it’s faulty, it can lead to components running too long or not long enough.

How to Check for Diagnostic Indicators

Most modern furnaces have a diagnostic indicator light system that is designed to provide information about the operational status of the furnace. These lights are typically located on the furnace control board and will be labeled as such. There may be two or three different lights, each having its specific meaning.

To check the diagnostic indicator lights, first, remove the furnace cabinet’s access panel and locate the furnace control panel. Once you’ve found it, locate the diagnostic indicator lights. If there is a problem, the indicator light(s) may be flashing in a specific pattern or may be off entirely. The code indicates the specific problem impacting the furnace, whether the issue is with the control board itself or another component.

If the indicator lights are flashing in a pattern, then consult your furnace manufacturer’s manual or the chart inside the access door for a key explaining what each code means. If the lights aren’t on at all, this means the board is not receiving power. 

If you are not confident with this process, it’s best to consult a licensed HVAC technician who can further diagnose and repair the issue. Any issues with a bad furnace control board require repair service from a professional to correct.

Get Help for Your Bad Furnace Control Board

A bad furnace control board can cause a range of issues with your HVAC system, and these issues can be dangerous if not addressed in a timely and efficient manner. If you notice any of the signs mentioned above, contact Grove Heating & Cooling to make an appointment for furnace repair service.

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