Lennox 85H75 Control Board

When you are troubleshooting a heat pump that refuses to initiate a defrost cycle or is experiencing excessive ice buildup on the outdoor coil, the Lennox 85H75 Control Board is a primary point of inspection. This OEM Lennox defrost bimetal control is designed specifically for high-efficiency series like the CHP15-511-1, serving as the logic center for monitoring coil temperatures and managing timing intervals. Unlike generic aftermarket boards, this HVAC replacement part ensures the proprietary bimetal sensor inputs are processed accurately to prevent premature or delayed defrosting, which can lead to compressor strain or reduced heating capacity. As a veteran-grade heat pump defrost board, it features a robust circuit design capable of handling the environmental stress of outdoor cabinet mounting. Integrating the Lennox 85H75 restores the system's ability to maintain optimal thermodynamic exchange during freezing conditions, ensuring the defrost cycle management operates within original factory parameters for residential and commercial applications.

• Direct OEM Compatibility: Engineered specifically for Lennox CHP15 series and select heat pump models, ensuring pin-to-pin wiring accuracy without modification.
• Precision Defrost Timing: Optimizes the initiation and termination of defrost cycles to eliminate ice accumulation while maximizing energy efficiency.
• Industrial-Grade Construction: Built with high-quality electrical components to withstand the voltage fluctuations and thermal cycling common in outdoor HVAC environments.
• Improved System Longevity: By regulating the defrost process correctly, it reduces mechanical stress on the compressor and outdoor fan motor.

How do I know if the 85H75 board is failing?
Technicians typically look for a "no-defrost" condition where the outdoor coil becomes a solid block of ice despite the bimetal switch closing. You should also check for 24V power at the board and verify that the defrost relay is engaging when the test pins are jumped.

Can this board be used to fix a heat pump that is not heating?
While the Lennox 85H75 controls the defrost function, if the heat pump isn't heating at all, you should first verify the reversing valve operation and refrigerant charge. However, if the "not heating" symptom is caused by an iced-over coil blocking airflow, replacing a faulty defrost board is the standard solution.

Is this a plug-and-play replacement for the 161R72?
Yes, the 85H75 is the designated replacement for several older Lennox part numbers, including the 161R72, providing the same form, fit, and function for the defrost control circuit.

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.