31377MC Air Flow Sail Switch MC Enterprises This replacement sail switch is designed for Atwood Everest and Excalibur Furnaces. It serves as an air proving device and ensures safe ignition by requiring 75% of the motor's rpm's before allowing ignition. When the switch paddle is pressed, there should be continuity through the switch. It is important to replace a sail switch with the exact same size. Common issues with these switches include bent paddles, loose wire connections, or obstructions between the paddle and switch contact. Compatible with: 7912-II, 7916-II, 7920-II, 8516-II, 8516-III, 8516-IV, 8520-II, 8520-III, 8520-IV, 8525-II, 8525-III, 8525-IV, 8531-II, 8531-III, 8531-IV, 8535-II, 8535-III, 8535-IV, 8935-DC-I, 8935-AC-I, 8940-DC-I, 8940-AC-I, 8935-DC-II, 8935-AC-II, 8940-DC-II, 8940-AC-II, 8935-DC-III, 8935-AC-III, 8940-DC-III, 8940-AC-III