QUESTION: My ruud
gas furnace goes out almost immediatly after ignition. Fan keeps going but no flame. Blows cold air. Will eventually reignite but goes out again right away. Any ideas? ANSWER: probably a clogged heat exchanger, clogged venting, or a dirty or faulty flame sensor. Flame sensors can be removed, lightly sanded with steel wool, washed with soap and water, dried, and reinstalled....