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3 led

  1. Pressure switch stuck open? 2 areas im looking @

    Hi, I've been searching for a few days & am unable to find what I'm looking for. I have a 7 year old furnace. lennox ultra 5 advantage. Went to turn on heat & nothing!! The led trouble code is 3 blinks = "Pressure switch stuck open 30 seconds or longer after call for heat. on/off switch...