A modern furnace runs a strict startup sequence, and knowing where the sequence breaks is most of the diagnosis. The thermostat calls, the inducer motor spins up to prove draft through a pressure switch, the hot surface igniter glows, the gas valve opens, the burners light, the flame sensor confirms fire, and only then does the blower deliver heat to the house. In Bel Air South, MD, the failures cluster at predictable points: an oxide-coated flame sensor, a hot surface igniter cracked from years of thermal cycling, a pressure switch that will not close because the inducer is weak or the condensate trap on a high-efficiency model has clogged, or a control board with a burned relay. Each one stops the sequence cold, and each one mimics the others from the hallway.
For air conditioning breakdowns, see AC Repair.
Warning Signs for Furnace Repair
Catching these issues early helps you avoid costly problems. Here are the most common indicators that it's time to call a professional:
- Rust streaks, soot, or water around the cabinet or flue
- Air moving through the vents that never gets warm
- Burners light, run a few seconds, then shut down repeatedly
- Frequent on-off cycling that never reaches the thermostat setting
- A bang or boom when the burners ignite late
- The furnace clicks and glows but the burners never light
- Grinding or high-pitched squeals from the blower
- Yellow, wavering burner flames where they should be sharp blue
Act Before It Gets Worse
What seems like a minor issue today can take out a compressor or heat exchanger tomorrow. Don't wait, call (443) 293-9740 and we'll take a look right away.
