Dometic Atwood 33082 Furnace Sail Switch With Bracket Upgrade KitThis is a replacement sail switch for select Atwood AFM and AFL Series Furnaces. 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 motors rpms. It ensures that the combustion wheel is rotating fast enough so that there is a proper air and gas mixture for smooth ignition.When the paddle of the switch is depressed, there should be continuity through the switch. If a sail switch needs to be replaced, it should be replaced with the exact same size. The most common problems with these switches are bent paddles, loose wire connections or an obstruction between the paddle and switch contact.Compatible withDometic Atwood Furnace AFM Series with Serial Numbers AFTER 72489156: AFMD25111, AFMD25121, AFMD25131, AFMD25141, AFMD25151, AFMD30111, AFMD30121, AFMD30131, AFMD30141, AFMD30151, AFMD35111, AFMD35121, AFMD35131, AFM