OEM Lennox Defrost Control Board — 97M81 / 100269-01

The genuine OEM Lennox 97M81 defrost control board (also identified as part 100269-01) manages the defrost cycle on your Lennox heat pump. Using inputs from the defrost thermostat and its own timing logic, the board decides when to reverse the refrigerant flow and energize the reversing valve to melt frost off the outdoor coil, then returns the unit to normal heating — protecting efficiency and preventing coil icing in cold weather.

When the 97M81 board fails, you may see the outdoor unit ice over and stay frozen, a heat pump that runs constant or excessive defrost cycles, no defrost at all, auxiliary/emergency heat that won't stage correctly, or the outdoor fan and compressor behaving erratically. A failed board can leave the system stuck, drive up energy bills, and reduce heating capacity.

OEM matters because the 97M81 is programmed with Lennox-specific defrost timing, relay logic, and terminal layouts matched to their heat pump control sequence. Aftermarket or universal boards often require rewiring and may not replicate the correct cycle behavior. This factory replacement drops in cleanly and restores proper, reliable defrost operation for your Lennox equipment.