A furnace has different working parts that can individually fail without proper HVAC maintenance. Defects or damage in one part, such as the heat exchanger, will adversely affect the whole system. If you are having problems with your HVAC, the following are signs that it could be the heat exchanger.

What Is a Heat Exchanger?

This component transfers heat safely within the HVAC system. Comprised of metal shells and/or tubes, they work by moving heat from one area to another.

In a gas furnace, the flue gas heats the metal; this, in turn, warms the air that passes over the exchanger. Damage within the heat exchanger can lead to elevated levels of carbon monoxide in the home, which is harmful to breathe or may be fatal in areas without ventilation.

What Are the Signs of a Damaged Exchanger?

1. Inconsistent Flame

HVAC-maintenanceYour furnace flame should be steady, strong, and blue in color. A yellow and/or flickering flame suggests that the heat exchanger is cracked, especially if the flickering gets worse when the fan is on. 

2. Visible Cracks or Holes

These occur as a result of the expansion and contraction of the furnace components from hot to cold. Chemicals and moisture can also corrode the parts of the heat exchanger and cause deterioration and let gases escape. If the furnace’s exterior exhibits wear, it’s time to schedule HVAC maintenance.

3. Unusual Smells

If the heat exchanger malfunctions, it can emit a strong, acrid odor similar to formaldehyde. Headaches or flu-like symptoms may occur as a result of the gases escaping from a damaged exchanger.

4. Soot

If you find soot on the inside of the furnace, this can indicate that the system isn’t working properly. Incomplete combustion may be the culprit, which is caused by a cracked heat exchanger or maladjusted burners.


If you need HVAC maintenance in the Nicholasville, KY, area, choose Stewart Air Conditioning & Heating. Since 1976, they have provided the greater Lexington area with quality heating and air conditioning repair, service, and installation. Call (859) 252-4945 to request a quote or visit the website to see a full list of products and services.