Lennox 81W03 Control Board

The Lennox 81W03 Control Board is the direct OEM replacement for the Lennox 17W70, 17W7001, and 81W0301 ignition control boards. As the central logic for your furnace, this integrated furnace control manages critical sequences, including hot surface ignition, flame sensing, and blower motor timing. It is engineered specifically for use in high-efficiency units such as the Lennox G40, G43, and ML180/ML193 series. When performing a field replacement, ensure the unit is equipped with a 95V igniter (part 75M21 or 100536-01), as this board is not compatible with 80V or 120V systems. Before condemning the existing Lennox circuit board, technicians should verify the integrity of the limit switches, pressure switches, and 24V transformer output. This factory-tested ignition board ensures precise data gathering from all safety components to optimize HVAC system performance and reliability. Proper installation requires matching the specific size code via the onboard 7-segment display to ensure the BTU and blower capacity align with your specific cabinet configuration.

• Exact OEM Fit: Direct Lennox 17W70 replacement designed for seamless mounting and terminal alignment in compatible furnace cabinets.
• Advanced Diagnostics: Features an onboard display to assist HVAC technicians in identifying fault codes like Error 203 for faster troubleshooting.
• System Optimization: Regulates the timing of the 95V hot surface igniter and blower speeds to maintain peak heating efficiency.
• Safety Integration: Continuously monitors flame signals and safety string components to ensure secure, reliable furnace operation.

• Is the 81W03 compatible with 120V igniters? No, this board is strictly designed for 95V ignition systems; using a different voltage igniter will result in component failure.
• What does Error Code 203 mean on this board? This indicates the board has not been programmed to the correct size code; technicians must use the push-button interface to match the furnace's BTU and blower capacity.
• Can I return this board if it doesn't fix my furnace? Most HVAC electrical components are non-returnable once installed, so verify that your pressure switch and igniter are functional before replacement.

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.