OEM Lennox Defrost Control Board — 56M85
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The genuine OEM Lennox 56M85 defrost control board manages the defrost cycle on your Lennox heat pump. In heating mode, frost and ice naturally build up on the outdoor coil. This board monitors coil temperature and elapsed run time, then reverses the system to melt accumulated ice and restore efficient heat transfer, energizing the reversing valve and auxiliary heat as needed.
Common failure symptoms: When the 56M85 defrost board fails, the outdoor unit may ice over completely, the heat pump can lose heating capacity, defrost cycles may run too often or not at all, or auxiliary heat may run excessively and spike energy bills. A blank display or failure to switch between heating and defrost modes also points to a faulty board.
Why OEM matters: The defrost logic, temperature thresholds, and timing intervals on this board are engineered specifically for Lennox heat pump systems. Aftermarket boards may use different defrost strategies that reduce efficiency or leave the coil iced. The factory 56M85 ensures proper terminal layout, direct fitment, and the precise defrost control your Lennox unit was designed around.
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