OEM Lennox Dual Pressure Switch Assembly — 36W77

The genuine OEM Lennox 36W77 dual pressure switch assembly verifies proper combustion airflow and venting before allowing your Lennox furnace to ignite. Working with the inducer motor, this dual-stage switch confirms that both draft pressures are within safe limits, ensuring exhaust gases are being vented correctly and preventing dangerous operation when airflow is blocked.

When a pressure switch fails or a vent is obstructed, the furnace will typically lock out and refuse to light, often flashing a pressure-switch fault code. You may also experience short-cycling, an inducer motor that runs but never triggers ignition, or intermittent no-heat calls. Cracked hoses, condensate blockages, or a stuck switch are common culprits behind these symptoms.

Installing the OEM 36W77 matters because the switch is calibrated to the precise pressure setpoints Lennox engineered for your furnace's venting system. An incorrect switch can allow unsafe combustion or cause persistent nuisance lockouts. This factory-spec dual pressure switch assembly ensures accurate airflow proving, reliable ignition, and full safety compliance with your Lennox equipment.