OEM Lennox Heat Exchanger Assembly — 57M99

Genuine OEM Lennox 57M99 heat exchanger assembly. The heat exchanger is the heart of your Lennox gas furnace — it transfers heat from the burning gas to the air moving through your ductwork while keeping combustion gases safely separated from the air you breathe. This factory-engineered assembly is built to the exact tolerances and metallurgy of your original Lennox unit for a proper, reliable fit.

Common failure symptoms: A failing heat exchanger often shows up as visible cracks or rust, a flickering or wavering burner flame, soot buildup, unusual odors, or a carbon monoxide detector alarm. Reduced heating performance and short cycling can also indicate a compromised exchanger. Because a cracked heat exchanger can leak carbon monoxide, replacement should never be delayed.

Why OEM matters: Lennox heat exchangers are designed with specific alloys, wall thicknesses, and pass configurations matched to each furnace model. Installing the genuine 57M99 assembly ensures correct combustion airflow, rated efficiency, and full compatibility with your Lennox safety controls — protecting both performance and your equipment warranty. Aftermarket substitutes rarely match these exact specifications.