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Blogs from November, 2018


If your heating system is making a ton of racket, these noises occur for a number of reasons. Whether it’s knocking or whistling, some noises are considered harmless while others indicate serious issues. It is important to understand the cause in order to figure out how the problem can be fixed. Although you may be able to repair the issues on your own, others will need the service of a professional HVAC technician.

The following are the most common furnace sounds and what they might mean:

  1. Loud bang or boom – Similar to hearing a gunshot being fired when you turn on your heating unit, a loud bang or boom often means there is gas build-up in the furnace, typically from dirty burners that delay the ignition. Such a loud noise could cause the heat exchanger to crack, which can be costly and dangerous. Additionally, a loud bang or boom could also be caused by air ducts expanding and contracting. In both cases, you need a professional to take a look and resolve the issue.
  2. Rattling – A rattling or vibrating sound could possibly mean loose components, such as a panel or screws. Prior to trying to tighten these parts, ensure your furnace is completely turned off. If it’s not a loose component, it could indicate there is heat exchanger crack or leak, which could release harmful carbon monoxide into your home. Contact an HVAC technician if the issue is a leak or crack.
  3. Screeching or squealing – A furnace makes a high-pitched sound of there is an immense amount of fiction involving moving components, often the blower motor. This noise is typically caused by a damaged or loose blower belt, unmaintained shaft bearings and other moving parts that have become dry due to wear and tear, or a blower motor malfunction. Call a professional if you hear this noise.
  4. Scraping metal – If you hear metal against metal, there might be an issue with your unit’s blower wheel. Either the blower wheel came loose and is constantly hitting the housing casing, a component became loose and hit the blower wheel, or the blower motor or wheel is damaged to the point of requiring repairs or replacement. Once again, an HVAC technician can handle the job.
  5. Rumbling – This noise often means dirty gas burners or a pilot light which requires adjustment since the heating unit hasn’t been maintained in quite a while. If the flame of your furnace is blue, even if there is a tiny yellow tip, then everything should be in working order. However, if it is any other color than blue such as red, orange, yellow, or green, this could be a hazard that requires a professional to take care of.

If you notice any of these noises coming from your furnace, contact our Los Angeles HVAC technician at H.L. Moe Co., Inc. and request a free estimate today.