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Lennox

OEM Lennox Control Board — 21J99

SKU: LNX-21J99 Brand: Lennox
$129.95 $169.95

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Texas CMBL #19328542014
SAM.gov Registered
Govt POs Accepted

The Lennox 21J99 is a genuine OEM control board that serves as the central command center of your Lennox heating and cooling system, coordinating ignition, blower operation, safety controls, and all other key functions. A faulty control board can cause a wide range of symptoms including failure to heat or cool, error or fault codes, components not responding, or complete system shutdown. This direct OEM replacement board is built to exact Lennox factory specifications, ensuring full compatibility and restoring proper system control in supported Lennox equipment.

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 Control Board fit my Lennox OEM Lennox Control Board — 21J99?
Yes. This is the factory-specified OEM control board for the Lennox OEM Lennox Control Board — 21J99. 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 control board on my Lennox OEM Lennox Control Board — 21J99?
Difficulty: Advanced (1–2 hrs)
Step 1: Turn off breaker. Step 2: PHOTOGRAPH all wire connections before touching anything. Step 3: Label each wire with tape. Step 4: Disconnect all wires, remove old board. Step 5: Mount new board, reconnect all wires matching your photo exactly. Step 6: Restore power and test all modes. Exact part number match is critical.
My HVAC system is completely dead. What could be wrong?
Completely dead HVAC (no LED on board) = failed control board or blown fuse. Check board fuse first (3A or 5A, costs $1–$5). If fuse is good and board has power but no LED, board is dead. Always photograph wiring before replacing.
Is this control board 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 control board?
OEM essential. Control boards are model-specific with precise firmware and connector layouts. Aftermarket boards rarely match all functions and can cause intermittent failures or safety issues. Always match the exact OEM part number.
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