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3 Signs Of A Faulty Furnace Control Board

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You might not think of your furnace as a computerized device, but the brains of a modern furnace are fairly high-tech. The control board is an essential component that manages all the major systems in your furnace, including power distribution, gas flow, and ignition.

As you might imagine, a failing control board is a serious problem that can lead to a furnace breakdown. This guide will explain three signs of a faulty furnace control board.

1. Cycle Interruptions 

Many homeowners first notice a problem with their furnace control board when changes appear in the way their furnace cycles. A faulty control board may cause your furnace to shut off unexpectedly or refuse to start if the board cannot complete the required circuit.

In some cases, a failing control board may result in your furnace running continuously. Relay switches on the board can get stuck in the open position due to dirt or corrosion on the board. Cleaning the board or replacing damaged relays and capacitors is possible, but it is more cost-effective to simply replace the board.

2. Burn Marks on the Board

An unexpected power surge can sometimes overload the furnace control board and cause it to burn out. You may notice visible signs of damage on the board if it has failed due to an electrical overload, arc, or short.

To inspect the control board, remove your furnace access panel and look near the blower motor at the base of the assembly. Call an HVAC contractor if you see black burn marks on the board or notice a burning smell.

3. Diagnostic Light or Code

If you have a newer furnace, it may feature a diagnostic panel in the assembly as well. Learning to read the error lights or codes on the diagnostic panel for your furnace model will make troubleshooting much faster and more reliable.

Many furnaces have a dedicated error code or light pattern to identify a faulty control board. You can refer to your furnace manual or the schematic behind the access panel for help interpreting the diagnostic codes.

Furnace control board failure is a relatively uncommon problem and one that is somewhat difficult to diagnose. If your furnace is short cycling or experiencing other power issues, a professional inspection can determine if the control board is to blame. Contact a local heating contractor so they can diagnose and repair your furnace control board if needed.