Even though the heating season thankfully is almost over, you should never ignore any of the strange noises you might hear while your furnace is in operation. Here are some of the most common noises and their causes.

Screeching or Squealing

This is one of the most common noises you will hear in a furnace, and this is especially true for furnaces that are more than 10 years old and those that have not received annual maintenance as required. Usually, this sound is due to a bad motor bearing, and the sound can be reminiscent of automobile brakes when they begin to fail. When you hear this noise, you should call a professional right away. The motor will need to be replaced because today’s motors have sealed bearings that cannot be serviced. If the problem is ignored, a failed bearing could cause a complete failure of your blower motor, and when this happens, you cannot heat your home.


A thumping sound, much like something stuck in a fan, typically indicates something is stuck in the blades of the blower or inside the furnace’s housing. If you hear this noise, you should stop using your furnace and contact a professional for advice. These repairs range from incredibly simple to quite complex, and if you attempt to locate and remove the object on your own, you could overlook a serious issue. Failing to repair the furnace and continuing to use the system anyway may lead to serious damage or even a complete system failure.

Popping Noises

Popping sounds are the most common sounds that come from furnaces. Usually, these noises are completely harmless because they come from the air ducts or even the air handler as the metal heats and expands, then cools and contracts. Relatively faint and irregular popping noises could very well be normal, but if the popping continues, if you hear a banging sound, or if it becomes loud, you should contact an HVAC mechanic for more help. These noises could indicate a serious issue with one or more furnace components and failing to address it may result in dangerous effects, such as carbon monoxide entering your home.

Scraping Sounds

If you hear a sound that reminds you of a metal utensil scraping against a metal pot, this is a pretty solid indicator that your blower wheel is faulty. It is a very loud and very obnoxious sound, and it reminds many people of nails on a chalkboard. The wheel itself may have worked its way loose, and if this is the case, it may scrape up against the blower casing when it is in operation. In other cases, it may be that the blower wheel or motor mount has broken. A loose blower wheel is a simple and inexpensive repair, but broken blower wheels and motor mounts – which can occur if you do not address a loose wheel – can become costly.

The heating season is coming to a close, but that is no reason to ignore strange sounds coming from your furnace. By addressing these issues now, you will be ready to stay warm during the next cooling season – and you’ll likely save money on repairs, too.