heating repair denver co area

Furnace noises and what they mean

If the unit produces noise, it means that it is working. However, the noise often means that the furnace system has issues. Noises differ and some of them are within norm, while others are the first sign that something is wrong and your furnace needs maintenance or even replacement of some parts. Every piece of a unit can break. However, in case of furnace, there are unpleasant consequences, as you can get cold without heating. Therefore, do not ignore the noise and do not let your furnace deteriorate while it needs a total overhaul.

If the noise of your furnace is irritating, we recommend reading our article. We will dive in the most common sounds in a furnace, explaining what is norm and what should alert you to call an expert to inspect the condition of the unit.

What Are Normal Furnace Noises?

When the unit starts its work, the norm is that it starts to produce some sounds. Operation noises may well be normal. However, in this case, they are balanced, silent (at the start) and quickly disappear as soon as the system accelerates to its regular capacity. The following can be considered regular noises.

Small Clicking

In a unit that is more than 5-10 years old, a small click is considered normal, if it starts before the heat begins to flow through the ducts into the room. Similar noise you can hear in newer furnaces as well. This is a kind of statement for a household that the heating process has started.

Popping in Your Ducts

Most often, you can hear small pops either when you have new unit, which has started operation for the first time, or you turned it on for the first time in a cold season. These pops in the channels evolved from the change of pressure inside while they need to align with it, expanding when the air comes from the heat pump.


In some cases, the heater chirping is the norm. Those sounds often occur at the beginning of the heating season, when, after a long break, the unit accelerates its capacity to its regular level.

Furnace Noises That May Mean Trouble

Not always, the sounds in the furnace are the norm. Often, an unusual noise that you never heard before means that something has gone wrong. Below, we will cover the most common furnace noises and what they mean for you to understand them and detect the issue inside the unit.


Quite often, rattling occurs when the furnace door is dragging and do not fit its frame. Often you can notice it yourself. If you have relevant skills and tools, then you can fit it. If the door works appropriately or you have fixed it, and the rattling continues, it means that some joints are loose. There are a lot of moving parts inside the furnace. The older is the unit, the more likely loose joints. In any case, to understand which part is rattling, you may want to call an expert.


This type of noise may indicate that the ignition lamp has broken or the furnace burner is clogged. Rumbling can occur during the combustion of accumulated dirt and oil. If the control lamp does not work, a specific rumbling sound may occur as well. Cleaning can be a solution as well as other works, which an expert can provide.

Booms or Bangs

If you begin to hear loud bangs in your furnace, be alert. Most often, a boom occurs because of the combustion of gas inside. In this case, the issue is the ignition, as the unit may not ignite from the first time, while a large amount of gas accumulates inside. When the furnace eventually starts working, it will burn the accumulated gas in an explosion with a distinct sound. In addition, the boom may occur because you did not clean it professionally for a long time.


Sharp noise may occur because the air filters inside the furnace are clogged and need cleaning or replacement. Whistling produces air that passes through the narrow holes in the filter with an effort. To prevent whistling in the house, maintain your furnace, clean it and change the filters regularly.

Thumping (a sharp noise)

A thumping with a sharp noise means that the major part assembly inside the furnace is slapping against the inner walls of the case. The issue may arise from the engine or the fan, which needs a checkup and a fix. In addition, the air bubbles inside the pipelines may produce thumping as well. Whatever the issue is, only the expert can detect it.

Grinding, Scraping, or Clanking

Often this sound in a running furnace indicates that the fan does not function properly.  If one part disunited from the other, there is friction between them, as they do not align. Only the expert can detect the issue during a checkup.

Knocking (similar to what you hear when knocking in the wood)

If you hear the clicks and pops once the furnace started running, then it is the norm. It is the way the air channels adapt to the amount of the air supplied. However, sometimes, those sounds can also indicate a breakdown. If the knock is quite sharp and loud, then the burner may be the issue because it needs cleaning. If your furnace is making a knocking sound, you should definitely call a professional; the issue can evolve in soot residue and a carbon monoxide leak.

Humming or Buzzing

The quiet to unnoticeable sound may be within the norm. Many furnace models are noisy. Be alert on the appropriate work of your furnace only if the noise is annoying. Its engine or fan may go out of function. However, the issue may be not that complex. Sometimes, the door is dragging, the filter installation is questionable, or the screw is loose. When any parts of the unit disunite, you can hear a buzz or hum.

Squealing and Screeching

Most often, such sounds indicate that the issue lays in fan operation. The engine belt can be displaced or broken. If it is too old, you might want to replace it with a new one. If it in satisfactory condition, making it more tight will do.

What Should You Do if You Hear These Noises?

The furnace may be noisy. Sometimes, this is normal, while in other cases it indicates a breakdown. Therefore, you need to distinct furnace noises and what they mean in order to cope with them in time, thereby protecting yourself from a potential accident that can turn into a real disaster if carbon monoxide will leak inside the room or your furnace will break down in the winter.

If your furnace produces unusual sounds that you have not heard before, be alert. In this case, consider the following steps:

  1. Detect the point of a noise. Make sure that the heater is the reason. In addition, distinct the type of the noise: is it a rattle, screeching, or clap.
  2. Understand the nature of the noise. Do you hear it once you turn on the furnace or when it accelerates the heat? In this case, read again the paragraph describing the noises within the norm.

If you are sure that the noise is definitely a sign of a breakdown, or if you want to double-check if the system is in full working capacity before the start of the heating season, then you should definitely contact the furnace maintenance professionals. Do not make DIY efforts if you do not have relevant experience. Contact the qualified service for professional diagnostics and fixing, if needed.

The Scariest Furnace Problems Can Be Silent

A sharp whistle, pops, rattle, and other annoying sounds do not always indicate a problem. The most serious breakdowns of the furnace comes out as an unpleasant noise. To prevent a serious issue with the unit, diagnose it systematically. If you cannot do it yourself, call the experts in heaters. For example, call our maintenance team.

In addition to the furnace diagnostics, we will detect the nature of the furnace that bothers you. Our maintenance team will check the heater, clean it and, if necessary, provide fixing works. Just call our managers.