Lennox 28W71 Sensor/Harness

For field technicians and contractors maintaining high-performance heat pumps, the Lennox 28W71 Defrost Ambient Sensor/Harness is a mission-critical OEM component designed for high-precision temperature monitoring. This 50-inch defrost sensor harness integrates two active thermistors (Sensors #1 and #2) to provide real-time coil and ambient data to the defrost control board. To streamline installation in specific equipment configurations, Lennox has engineered this assembly with a fixed 10K resistor in the third sensor position, simulating a stable temperature input where a physical third sensor is not required by the system logic. Using 24 AWG wiring and standard AMP terminations, this Lennox 101334-02 replacement ensures the unit initiates defrost cycles only when necessary, preventing ice accumulation on the outdoor coil while maintaining optimal seasonal energy efficiency ratios.

• OEM Compatibility: Precision-fit for Lennox 14HPX and XP14 series heat pumps, ensuring reliable communication with the control board.
• Simplified Wiring: Features a factory-installed 10K ohm resistor in place of Sensor #3 to eliminate compatibility errors in specific control board revisions.
• Durable Construction: Built with UL2468 rated 24 AWG black wiring, rated for 80°C to withstand the rigorous thermal cycling of outdoor condenser units.
• Accurate Defrost Timing: Provides the exact resistance values needed to prevent premature or delayed defrost cycles, protecting the compressor from liquid slugging.

Which models are compatible with the 28W71 sensor?
This harness is primarily utilized in Lennox heat pump systems like the 14HPX and XP14, but it also cross-references as Lennox 101334-02 for various other residential units requiring a 50-inch lead.

Why is there a resistor instead of a third sensor?
This design choice by Lennox allows the harness to work with control boards that expect three inputs. The 10K resistor provides a "dummy" signal, allowing the board to operate using the primary coil and ambient sensors without triggering a fault code.

What are the symptoms of a failing defrost sensor?
Contractors typically replace this part when the outdoor coil is completely encased in ice or if the unit is staying in defrost mode too long. Inaccurate resistance readings from a degraded Lennox ambient sensor often lead to these efficiency losses.

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Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.