A furnace that clicks, hums, then falls silent without heat is failing somewhere in its ignition sequence. On newer systems the usual culprits are a cracked or worn hot surface ignitor, a flame sensor coated in oxide so it cannot prove flame, or a pressure switch that will not close because the flue or condensate line is blocked. On older standing-pilot units, a pilot that lights but will not stay lit usually points to a failing thermocouple or a draft reaching the pilot assembly.
These faults follow a diagnosable order and a professional will work through it rather than replacing parts on guesswork. Repeated ignition lockouts should not be reset over and over, since each attempt puts unburned gas into the chamber. Pro HVAC connects homeowners in Gratis, OH with HVAC professionals. Call (321) 463-9811.
