OEM Lennox Pressure Switch — 26W85

The genuine OEM Lennox 26W85 pressure switch is the venting safety control that tells your Lennox furnace it is safe to light. It monitors the negative pressure produced by the draft inducer and closes its contacts only when the vent path is clear, allowing the control board to energize the gas valve and begin the ignition sequence.

When the 26W85 fails, you'll often see the furnace lock out on a pressure fault, cycle the inducer without ever firing, or ignite and then shut down within seconds. Blocked sensing tubing, a torn diaphragm, condensate trapped in the port, or worn contacts are the usual culprits, and each one keeps the safety circuit from proving proper draft.

Pressure switches are calibrated to a precise trip point for the specific inducer and vent configuration of each Lennox model, which is why an OEM replacement is the right choice. An off-spec aftermarket switch can permit the burner to fire under poor venting or trigger false lockouts on an otherwise healthy furnace. The factory 26W85 delivers the exact set point Lennox engineered, protects your warranty, and keeps combustion safe and reliable.