OEM Lennox High Pressure Switch — 11F05

The genuine OEM Lennox 11F05 high pressure switch is a critical safety control that monitors refrigerant discharge pressure and shuts the compressor down before dangerous overpressure conditions can cause damage. Installed in the high side of your Lennox condensing unit, it opens the control circuit when pressure exceeds its factory setpoint, protecting the compressor, coils, and other components from failure caused by a blocked condenser, dirty coil, or overcharge.

Common symptoms of a faulty 11F05 include nuisance high-pressure lockouts, a compressor that trips repeatedly on hot days, the unit failing to start, or a switch that no longer resets after cooling down. A switch that is stuck open leaves you with no cooling, while one stuck closed removes vital overpressure protection.

OEM matters here because a pressure switch is a life-of-the-compressor safety device — the correct trip and reset pressures must match your Lennox system exactly. The 11F05 is calibrated to factory specifications with the correct fitting and electrical connection, ensuring reliable protection and a proper fit. Installing a mismatched aftermarket switch risks either false trips or, worse, a compressor left unprotected against destructive pressures.