Also referred to as a “control board,” the circuit board essentially serves as the brains of air conditioners, heat pumps, and furnaces, as they coordinate the sequence of operational events that occurs with every cooling or heating cycle. Some circuit boards also monitor the operational health of HVAC systems and provide warnings when its sensors detect a potential problem. Typically included as part of the air handler, some systems include them in the condensing system. Circuit boards tend to be highly reliable, though they can be damaged by power surges and other electric anomalies. HVAC circuit board problems are usually resolved through replacement rather than repair.