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Lennox

OEM Lennox Ventostat CO2/RH/Temp Wall-Mount LCD Sensor White — 77N39

SKU: LNX-77N39 Brand: Lennox
$24.95 $34.95

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Texas CMBL #19328542014
SAM.gov Registered
Govt POs Accepted

The Lennox 77N39 is a genuine OEM Ventostat wall-mount transmitter featuring a built-in LCD display that provides real-time visibility into CO2 concentration, relative humidity, and temperature levels within your Lennox-controlled environment. If your demand-controlled ventilation is performing erratically, displaying incorrect air quality readings, or failing to respond to occupancy changes, this sensor may require replacement. The white-finished unit is a direct OEM replacement designed for seamless integration with compatible Lennox ventilation and zoning systems.

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 Sensor fit my Lennox OEM Lennox Ventostat CO2/RH/Temp Wall-Mount LCD Sensor White — 77N39?
Yes. This is the factory-specified OEM sensor for the Lennox OEM Lennox Ventostat CO2/RH/Temp Wall-Mount LCD Sensor White — 77N39. 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 sensor on my Lennox OEM Lennox Ventostat CO2/RH/Temp Wall-Mount LCD Sensor White — 77N39?
Difficulty: Easy (10–15 min)
Step 1: Turn off power/gas. Step 2: Open furnace panel. Step 3: Locate flame sensor rod near burners. Step 4: Remove single mounting screw. Step 5: Clean rod with 400-grit sandpaper until shiny (or replace). Step 6: Reinstall and tighten. Most common furnace repair — saves $150–$300 vs technician.
My furnace lights then shuts off after a few seconds. Why?
Furnace lights then shuts off after 3–10 seconds = dirty flame sensor in 90% of cases. The sensor can’t detect flame through oxidation buildup. Fix: clean with 400-grit sandpaper (free, 15 min). If cleaning doesn’t work, replace the sensor.
Is this sensor 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 sensor?
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