What usually causes no heat
Most no-heat calls trace back to a small set of parts: a dirty flame sensor, a failed igniter, a blocked condensate drain on a high-efficiency furnace, a pressure switch, or a control board. A clogged filter causes more problems than people expect, because the furnace overheats and shuts itself off for safety.
We test each part before we name a problem. Swapping parts until the furnace runs is how a simple repair turns into an expensive one.

