OEM Lennox Pressure Switch — 26W84

The genuine OEM Lennox 26W84 pressure switch is a factory safety device that verifies adequate combustion-air draft in your Lennox furnace before the burners are permitted to ignite. It reads the vacuum generated by the inducer motor and closes only when venting is sufficient, ensuring the furnace never fires under conditions that could allow flue gases to spill.

A worn or defective 26W84 commonly produces a furnace that runs the inducer but won't light, a repeated ignition lockout, or a burner that flames briefly then extinguishes. Diaphragm fatigue, plugged or cracked sensing lines, moisture in the pressure port, and pitted contacts are the typical failure modes, and any of them cause the control board to register an open safety circuit.

Lennox sets each pressure switch to a model-specific trip point tied to its inducer and vent design, so an OEM replacement is important for safe, dependable operation. A generic switch with the wrong rating may bypass the very protection this part provides or create nuisance faults on a good system. The factory 26W84 matches the engineered set point exactly, keeps your warranty intact, and maintains the furnace's built-in safety response.