
Furnace Making Loud Noise
A boom at ignition or a scraping blower means a part is under real stress, and calling before it lets go is far easier than calling afterward.
When this becomes an emergency
- A hard boom or thump comes from the furnace a moment after the burner lights.
- A high metallic screech starts up whenever the blower runs.
- Something is scraping or knocking inside the cabinet and getting worse week to week.
- The noise has changed character recently rather than always having been there.
What a pro does
Furnace noises sort into a few families, and the family tells you where to look. A delayed ignition boom means fuel gathered in the burner chamber before it caught, and every one of those pressure pulses works against the heat exchanger, which is why techs treat that sound as urgent rather than cosmetic. Screeching usually comes from a bearing or a belt. Scraping is different again: a blower wheel that's shifted on its shaft or lost a balance weight will drag against the housing, and that gets diagnosed by pulling the assembly and turning it by hand rather than by listening from across the basement. Panels and duct straps buzz too, and those are cheap to rule out first.
Frequently asked questions
Furnace Making Loud Noise?
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