Which signs may indicate that a gas furnace's heat exchanger is cracked?

The signs that indicate a gas furnace's heat exchanger is cracked include rust buildup, unusual odors, or visible cracks. Rust buildup often occurs in areas of the heat exchanger where moisture can accumulate, signaling potential deterioration. Unusual odors, particularly a hissing or odor reminiscent of gas, may indicate that combustion gases are escaping due to a crack. Visible cracks in the heat exchanger are a more direct indication of damage that can compromise the system's efficiency and safety.

These indicators emphasize the necessity of regular maintenance and inspections to ensure that the heat exchanger remains intact and functioning properly. It’s crucial to address any signs of damage promptly, as a cracked heat exchanger can lead to serious safety hazards, including carbon monoxide leaks.