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Lennox

OEM Lennox Heat Exchanger Assembly — 36M71

SKU: LNX-36M71 Brand: Lennox
$399.95 $549.95

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Texas CMBL #19328542014
SAM.gov Registered
Govt POs Accepted

The genuine OEM Lennox 36M71 (interchange R20431903) heat exchanger assembly is the core combustion component of your Lennox gas furnace. It transfers heat from the burning gas to the air circulating through your home while keeping combustion byproducts safely separated from the breathable airstream. This assembly is engineered to the exact tolerances of the original Lennox furnace it was designed for, ensuring proper airflow, correct temperature rise, and rated efficiency.

Common failure symptoms: A failing or cracked heat exchanger often shows up as a flickering or shifting burner flame, rust or corrosion streaks on the metal, soot buildup, unusual odors, or the furnace short-cycling on the flame-rollout or limit switch. A cracked exchanger can also allow carbon monoxide to enter the airstream — making prompt replacement a safety priority.

Why OEM matters: Because a heat exchanger is a safety-critical, combustion-sealed part, only a genuine Lennox 36M71 guarantees the precise fit, metal gauge, and weld integrity your furnace requires. Aftermarket substitutes risk poor sealing, premature cracking, and voided warranties. Choose the factory part for a safe, code-compliant, long-lasting repair.

Shipping Information

  • Orders placed before 3PM CST ship same business day
  • Standard delivery: 2-5 business days
  • Express shipping available at checkout
  • Free shipping on orders over $75
  • Tracking number emailed upon shipment

Return Policy

  • 30-day returns on unused parts in original packaging
  • Electrical parts (capacitors, contactors, control boards) are final sale once installed
  • Email info@nationalhvacparts.com to initiate a return
  • Refunds processed within 5-7 business days

Frequently Asked Questions

Does this Heat Exchanger fit my Lennox OEM Lennox Heat Exchanger Assembly — 36M71?
Yes. This is the factory-specified OEM heat exchanger for the Lennox OEM Lennox Heat Exchanger Assembly — 36M71. It is a direct drop-in replacement that fits without modification. Always verify the model number on your equipment nameplate before ordering.
How do I replace the heat exchanger on my Lennox OEM Lennox Heat Exchanger Assembly — 36M71?
Refer to your equipment service manual for model-specific steps. General approach: turn off power, photograph connections, remove old part, install new part, restore power and test. For gas components, hire a licensed technician. Email info@nationalhvacparts.com for guidance.
What symptoms mean I need a new heat exchanger?
Common symptoms: unusual noises, intermittent operation, complete failure, or visible damage. Visit our diagnostic hub for symptom-based troubleshooting.
Is this heat exchanger compatible with Bryant or Payne too?
Many Lennox parts are cross-compatible with Bryant and Payne since all three brands are manufactured by Carrier Global Corporation. The same physical part is often used across brand labels with different model numbers. To verify: check your Bryant or Payne equipment service manual for cross-compatible part numbers, or email info@nationalhvacparts.com with your model number.
Should I use OEM or aftermarket for my Lennox heat exchanger?
OEM recommended for reliability and warranty compatibility. OEM parts match exact factory specifications for proper fit, performance, and safety. While aftermarket alternatives cost less upfront, the risk of improper fit and reduced lifespan usually makes OEM the better value long-term.
How fast does National HVAC Parts ship?
Orders placed before 3:00 PM CST ship the same business day. Standard delivery is 2–5 business days anywhere in the continental United States. Express shipping available at checkout. We ship from Houston, TX to all 50 states. 30-day return policy on all parts.
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Mike Rivera
HVAC Parts Specialist — Online