HVAC Repair Tips


Furnaces are used constantly in winter and due to this, they can run into problems as well. A heat exchanger is an essential part of a furnace and if it’s damaged, you will not only have to deal with poor heating, but your health can also be at risk. Therefore, any issue with the heat exchanger must be fixed immediately by qualified furnace repair services. Let’s know how to spot a damaged heat exchanger.

What Is A Heat Exchanger?

A heat exchanger is a set of metal coils in a furnace. The burners make the heat exchanger (the metal coils) hot. Meanwhile, air is blown over the heat exchanger using a blower fan. The air becomes hot and goes to the ductwork and warms up your house.

Signs Your Furnace Heat Exchanger Is Cracked

The most common damage seen in heat exchangers is cracks, however, there can be tiny holes as well due to rust, corrosion, or any other factor.

Furnace Isn’t Blowing Hot Air

This is not always noticed in furnaces with a damaged heat exchanger, but there can be a variation of this like decreased performance of the furnace.

Usually, when a heat exchanger is cracked or damaged, the furnace may stop working and you won’t feel hot air coming from vents anymore. If it happens, this is a blessing in disguise because in case a furnace keeps working with a cracked heat exchanger, harmful gasses can leak into your house and cause various health problems.

Beware that a furnace not warming up your house can be a sign of other furnace problems as well. If your furnace doesn’t blow warm air, don’t immediately consider that it’s because of a damaged heat exchanger. Something like a clogged filter, dirty furnace, or any other problem with the furnace will also trigger this. So, as we always suggest, couple this symptom with other signs below.

The Flame Color Is Yellow

The color of the gas burners’ flame in your furnace should be blue. This is because whenever a combustion process occurs in a sealed chamber, it will create a blue flame. It shows that the combustion process is taking place without any problems.

However, if the flame color is yellow, it can be due to a damaged heat exchanger. However, a yellow flame can be because of dirty burners as well. So, the best thing to do is to call in an expert who can check why your furnace flame is yellow instead of blue.

Loud Noises

Furnaces make a standard noise when operating. But if you hear loud or unusual noises, something is wrong. Different types of furnace noises show different sorts of problems. A booming or explosion noise may mean that the gas burners are dirty or not working properly due to any other reason.

Similarly, a rattling noise usually hints at a cracked heat exchanger. As the metal contracts and expands due to heat, the cracked parts become louder and you hear a rattling or banging noise. However, it may be due to loose parts as well.

Whichever noise you hear, you should not ignore it if it’s not the regular furnace noise. Have an expert inspect your furnace to determine what is causing the noise.

A Strong Chemical Odor Coming From The Furnace

Mostly, a damaged heat exchanger doesn’t cause any smell even though it releases harmful gasses like carbon monoxide into your house. However, sometimes, a damaged heat exchanger may develop a strong chemical odor that is due to formaldehyde fumes.

No Smell, But Your Carbon Monoxide Detector Goes Off

This is a huge sign of a cracked heat exchanger. We explained earlier that a damaged heat exchanger releases carbon monoxide. It’s an odorless, colorless, and toxic gas. Inhaling it can cause various health problems and, in severe cases, even death.

This is the reason carbon monoxide detectors are used so you’re alarmed in the event of a CO leakage. So, if your carbon monoxide detector goes off, you should shut down your furnace and consult an expert. They will check your furnace and it will likely be an issue with the heat exchanger.

This also highlights the importance of a working carbon monoxide detector. Because you might think that it’s working when it’s out of order and won’t detect a CO leak if it occurs. It creates a serious health hazard.

So, check your CO detector once a month. Use the test button on your CO detector to test it. Moreover, clean the exterior of the detector regularly and change its batteries within 6-12 months. And buy a new one if your CO detector is older than 5-7 years.

Health Problems In Yourself Or Your Family

Even with the CO detector maintenance, you should keep an eye on the health of yourself and your family members. If you or any other in the house feel nausea, fatigue, flu, dizziness, and similar symptoms for no reason, find a doctor and also have your furnace and other appliances checked. Along with that, inspect your CO detector.

Soot Buildup Inside The Furnace

The combustion process is carried out in a proper manner inside a furnace. Due to clean burning, no soot is produced with combustion. But if the heat exchanger is cracked, the burning process will be inadequate leading to soot buildup.

Soot is a black substance that you might find inside your furnace if its heat exchanger is cracked. So, if you do find it, you should get a professional to check your furnace and its components including the heat exchanger.

Water Pooling Around The Furnace

Water leakage from a furnace can be due to various reasons, but one of them is a damaged heat exchanger. This symptom of a damaged heat exchanger is more common in high-efficiency furnaces that have two heat exchangers. However, there could be a water leakage in standard furnaces with a single heat exchanger as well.

But keep in mind that a furnace water leakage could be due to other things as well like an issue with the furnace humidifier.

Corrosion And Cracks In Furnace Components

A damaged heat exchanger can cause problems with other components of your furnace as well. You might notice corrosion or cracks in parts of your furnace like the inducer motor. Corrosion seen outside suggests that the components may be corroded much from the inside. So, if you see corrosion or cracks on any part of the furnace, get help from an expert.

What You Should Do If Your Heat Exchanger Is Damaged?

Once your expert detects that the cause of your furnace problems is a cracked heat exchanger, you have only three choices.

  • If the damage to the heat exchanger is small, it could be repaired.
  • You will need to replace the furnace.
  • You will need to replace the furnace.

If your heat exchanger can’t be repaired, the replacement of a heat exchanger is costly. Many experts suggest replacing the entire furnace rather than replacing the heat exchanger of your existing furnace.


A damaged heat exchanger can be a huge problem because it damages the furnace and can also put your family’s life in danger with CO leakage. If you notice any of the above signs, consult an HVAC repair service McLean immediately.


Your email address will not be published. Required fields are marked *