Check the listing for details. For Atwood 31094 Sail Switch New. Condition: New. Listed at 13.17 USD. RV Furnace Air Flow Sail Switch Replacement 31094 AFM AFLD AFLA DFMD Series Product Description [How to know you need to replace]---When your would run normally, if you hear the igniter begin to fire, then the furnace would light, then immediately go out.Maybe you can consider the problem of the sail switch. [How does it work]---The sail switch is an air proving device. It is a safety component that will not let ignition occur until it sees 75% of the motor’s rpm’s. It ensures that the combustion wheel is rotating fast enough so that there is a proper air and gas mixture for smooth ignition. [Compatible models]---Furnace AFM Series with Serial Numbers BEFORE 72489156: AFMD25111, AFMD25121, AFMD25131, AFMD25141, AFMD25151, AFMD30111, AFMD30121, AFMD30131, AFMD30141, AFMD30151, AFMD35111, AFMD35121, AFMD35131, AFMD35141, AFMD35151. [Compatible models]--- Furnace AFLD Series with Serial Numbers BEFORE 72991127: AFLD35111, AFLD35121, AFLD35131, AFLD40111, AFLD40121, AFLD40131. [Compatible models]---AFLA Series with Serial Numbers BEFORE 81689155: AFLA35211, AFLA35221, AFLA35231, AFLA40211, AFLA40221, AFLA40231. [Compatible models]---Furnace DFMD Series with Serial Number BEFORE 72489156: DFMD25111, DFMD25121, DFMD25131, DFMD25141 and DFMD25151. Replace 31094 RV furnace air flow sail switch.