The MC 31377MC is a replacement low air flow sail switch designed for select Atwood Everest and Excalibur RV furnaces. This critical safety component serves as an air proving device that prevents furnace ignition until proper airflow is detected.
How It Works:
The sail switch monitors combustion blower operation and will not allow ignition to occur until it detects 75% of the motor's RPM. This ensures the combustion wheel is rotating fast enough to create the proper air and gas mixture for smooth, safe ignition. When the paddle is depressed by adequate airflow, continuity is established through the switch, allowing the furnace to proceed with the ignition sequence.
Key Features:
- Direct replacement for Dometic/Atwood part number 31377
- Prevents ignition without adequate airflow for safety
- Monitors blower motor speed to ensure proper combustion air mixture
- Compact design for easy installation in tight furnace compartments
- Made in the USA with quality craftsmanship
- Backed by MC Enterprises limited 1-year warranty
Compatible Furnace Models:
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
Installation Notes:
Sail switches must be replaced with the exact same size as the original. Common issues with sail switches include bent paddles, loose wire connections, or obstructions between the paddle and switch contact. Always inspect mounting location and ensure paddle moves freely before installation.
