Should My Furnace be Making Strange Noises? 

Should My Furnace be Making Strange Noises
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Your dog can hear them; odd sounds from your furnace that indicate that something needs changing, lubricating, tightening, or cleaning. Let’s walk together down the not-so-warm and fuzzy alley of; “Noises my furnace shouldn’t be making.”



If you experience any strange noises from your furnace, you should turn it off and look into arranging furnace maintenance. Call our office manager, Vanessa, at (519) 900 9960 to arrange a time for a visit and inspection from our team. 

Meet our caring team here and read some of our five-star reviews at the bottom of our Heating Page. We are a customer-service-oriented local furnace and air-conditioning company serving London and St. Thomas. 


Noises my furnace shouldn’t be making.”


1. Loud humming or buzzing

The determining word here is loud. A low hum or a pleasant whirring accompanies the start-up of a furnace cycle.

However, aggressive humming or buzzing usually has something to do with an electrical aspect of a motor:

  • The blower motor or its capacitor is no longer pushing air through the ductwork
  • A failing transformer. 
  • The motor or capacitor may need to be lubricated.
  • The blower fan may have worn out.
  • Gas burners may be dirty and need adjustment or replacement.


2. Clunking or knocking

If you are experiencing a low-level knocking or clunking sound, it may have to do with a fan issue.

If a blower fan is misaligned, the blades can hit the wall of the furnace. Other possibilities for clunking and knocking sounds:

  • A fan belt has split or cracked and hits something as it rotates.


3. Squealing or whistling

Whistling is usually a sign of obstructed airflow; changing a clogged air filter may fix the problem and can quickly be done by you.

Air filters are relatively inexpensive and make a huge difference to the performance of your furnace performance, and replacing them is always a good choice. You should change your air filters at least twice monthly; some require monthly changes.

Pay attention to arrows indicating the direction that your air filter must be installed. What else causes squealing or whistling?

  • Obstructed vents.
  • Dirty ductwork.
  • Squealing sounds may be a sign of a damaged belt.


4. Screeching or scraping

If the screeching reminds you of metal being pulled across metal, that could be exactly what is happening:

  • The blower fan may have loosened, allowing its blades to drag across the furnace wall.
  • Other parts may have come loose.


5. Rattling

The heat exchanger is an essential component of your furnace. It’s where the cool outside air is heated before being blown through the ductwork in your home.

As your furnace ages, the continuous vibration of its parts can eventually loosen nuts that can be tightened. A high-pitched rattling heard immediately after the furnace engages could also indicate heat exchanger leaks. Other possibilities of rattling are:

  • Loose bearings in the blower motor.
  • Panel bolts that wiggle loose.
  • Unfastened ductwork connectors.
  • A worn blower fan belt.


6. Loud and not-so-loud banging

If you hear a loud bang from your furnace when it starts, it usually indicates a problem with its ignition.

At the beginning of its cycle, your furnace receives a signal from the thermostat, the gas valve opens, and the pilot light or electrical ignition system ignites the gas immediately.

If the ignition is faulty, an extra amount of gas builds up in the combustion chamber so that when the ignition does happen, it creates a loud boom due to gas build-up. Other reasons for a banging sound:

  • Ignition burners may be clogged or dirty.
  • The gas pressure may be low.
  • The air-to-gas mix is unbalanced.
  • On older furnaces, the pilot light may be broken.
  • Contraction and expansion of your ductwork. The thin metal expands with the heat, making a slight banging sound as it contracts. You’ll hear it in various places throughout the house, not where the furnace is situated. Thicker-walled ducts or switching to round ductwork will alleviate the problem.


7. Clicking

Clicking sounds are associated with a failure in the ignition system:

  • There may be a bad valve.
  • A faulty ignition board.
  • A broken flame sensor.
  • The pilot light may be out.
  • On older furnaces, the thermocouple is broken.
  • A broken fan motor with loose bearings can sound like clicking.


We believe in “good old-fashioned people-valued service.” 

-Peter Inch & Associates Heating + Air Conditioning will never try to sell you anything you don’t need. Our client testimonials, proudly shown at the bottom of our heating and cooling pages, say it all.




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