A Lennox furnace control board is the central hub for managing and coordinating the various functions of a Lennox furnace. It acts as the "brain" of the furnace, regulating components like the blower motor, gas valve, and ignition system. The control board ensures efficient operation by processing signals from the thermostat and safety sensors, such as the flame sensor and limit switch. If a problem arises, the control board often displays diagnostic error codes to aid in troubleshooting.