Furnace Noise Diagnosis — Complete Guide to Every Sound

Published: July 21, 2026 — BC Wide Home Services Ltd, doing business as BC Wide Heating & Air Conditioning — Greater Vancouver, BC

Banging or Popping

Loud bang at ignition: delayed ignition — gas accumulates before lighting. A technician should clean the burners and check gas pressure. Popping from ducts: normal metal expansion. Pinging: heat exchanger metal expanding — if persistent, have the heat exchanger inspected for cracks.

Screeching or Squealing

High-pitched screech from the blower area: worn blower motor bearings. The motor will eventually seize. Replacement costs $500-1,200. A squealing belt on older belt-drive furnaces: replace the belt ($50-150) or tighten if adjustable.

Humming or Buzzing

Hum from the furnace: transformer vibration (normal in some models) or a failing capacitor. Buzzing from the contactor (central AC): pitted contactor contacts. Rattling: loose panels, debris in blower, or loose duct connections. Tighten all screws and check for loose duct straps.

Related Services

Safety Reminder

If you smell gas, suspect carbon monoxide or believe there is an immediate danger, leave the property and contact emergency services or the appropriate gas emergency authority. Do not remain inside — exit the building immediately and call for help from outside.