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Lennox

OEM Lennox Limit Control S21 — 78L67

SKU: LNX-78L67 Brand: Lennox
$19.95 $28.95

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Texas CMBL #19328542014
SAM.gov Registered
Govt POs Accepted

The Lennox 78L67 Limit Control S21 is a genuine OEM high-limit safety device engineered to sense plenum or heat exchanger temperatures and cut power to the burner assembly when temperatures exceed safe operating thresholds, protecting your Lennox furnace from damage. A failing limit control may cause symptoms such as frequent short cycling, the blower running continuously without heat, or a complete furnace lockout. This OEM replacement part provides exact-fit compatibility and reliable performance for the Lennox systems it was designed to serve.

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 Limit Switch fit my Lennox OEM Lennox Limit Control S21 — 78L67?
Yes. This is the factory-specified OEM limit switch for the Lennox OEM Lennox Limit Control S21 — 78L67. 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 limit switch on my Lennox OEM Lennox Limit Control S21 — 78L67?
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 limit switch?
Common symptoms: unusual noises, intermittent operation, complete failure, or visible damage. Visit our diagnostic hub for symptom-based troubleshooting.
Is this limit switch 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 limit switch?
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