The circuit / control board functions as the brain of your furnace, controlling the gas valve, hot surface igniter and flame sensing circuit. A more efficient type of board, known as the integrated furnace control, also controls the furnace blower in both air conditioning and heating modes. LED’s on the board show system status, performance and provide diagnostic information. Blinking codes on the furnace panel will indicate whether your board has experienced a parts failure.
Examples of failures may relate to a limit switch, pressure switch or be a flame safety problem. AVOID searching to buy ANY electro-magnetic part for your circuit board that relates to flame safety. It is best to replace the unit to ensure a safe furnace in your home.
Circuit boards contain black boxes called electro-mechanical relays that turn on the fan, turn on the inducer and hot surface igniter. These relays wear out over time and replacement is necessary. All manufacturers recommend that a circuit board be replaced if the board has been wet, varying from a flood to a mere splash, regardless whether the board is in working condition.