jumptrout Posted February 25, 2013 Share Posted February 25, 2013 Coleman gas furnace model.#7956.Need manual if available.Furnace fires,heats up for fan relay to come on.Fan cycles.Unit cools quickly and fan stops.Burner stays lit and repeats above sequence.Fan limit switch is a 110 degree -20 degree.Heat exchanger in good condition.Flue not blocked. Link to comment Share on other sites More sharing options...
jumptrout Posted March 7, 2013 Author Share Posted March 7, 2013 Manual no longer needed.I deciphered the problem.Furnace had been operating several years with no drip leg installed on the gas supply.The gas nozzle and orifice had become 50% restricted with a rust buildup.Although outlet pressure read good on the manometer,the gas pressure reduced greatly at the burner causing low flame and insufficient heat.A thorough cleaning of the nozzle and the addition of a drip leg has this furnace working like new. 1 Link to comment Share on other sites More sharing options...
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