The International Comfort Product 1173636 Defrost Control Board is an essential feature of HVAC systems, especially heat pumps. This specific board is in charge of controlling the defrost cycle, which guarantees peak performance during the winter. Frost and ice buildup on a heat pump's external coils during colder months may reduce the unit's effectiveness. https://www.partshnc.com/international-comfort-products-1173636-defrost-control-board