What are the specs for this Control Board?

The correct replacement for Lennox model OEM Lennox Low Ambient Control Sensor — 55W73 is this exact part. It is the factory-specified replacement with exact OEM specifications. Using a part with different specifications can cause equipment damage or void your warranty. You can verify this by checking the data plate on your Lennox equipment which lists the model number OEM Lennox Low Ambient Control Sensor — 55W73.

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OEM Lennox Low Ambient Control Sensor — 55W73

Name: OEM Lennox Low Ambient Control Sensor — 55W73
Brand: Lennox
SKU: LNX-55W73
Price: 39.95 USD
Availability: InStock

SKU: LNX-55W73 Brand: Lennox

$39.95 $54.95

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The genuine OEM Lennox 55W73 low ambient control (part reference K1SNSR33CS1) allows your Lennox condensing unit to run safely in cold outdoor temperatures by monitoring conditions and cycling the outdoor fan to maintain proper refrigerant head pressure. Low ambient controls are essential for applications requiring year-round cooling — such as server rooms and other continuous-load spaces — where the system must operate well below normal seasonal temperatures.

Common failure symptoms include the outdoor unit tripping on low-pressure lockout in cool weather, the condenser fan failing to cycle, poor or lost cooling when outdoor temperatures drop, or ice forming on the coil. Sensor drift, moisture damage, and electrical faults are typical causes.

Why OEM matters: the 55W73 is matched to the pressure and temperature setpoints of your specific Lennox condenser. Generic controls may cycle the fan at incorrect thresholds, risking compressor damage or nuisance shutdowns. Install the factory-specified component to protect the compressor and keep low-ambient cooling reliable and efficient.

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

OEM Lennox Low Ambient Control S...

$39.95

Frequently Asked Questions

Does this Control Board fit my Lennox OEM Lennox Low Ambient Control Sensor — 55W73?

Yes. This is the factory-specified OEM control board for the Lennox OEM Lennox Low Ambient Control Sensor — 55W73. 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 Low Ambient Control Sensor — 55W73?

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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OEM Lennox Low Ambient Control Sensor — 55W73

Shipping Information

Return Policy

Frequently Asked Questions