OEM Lennox High Pressure Switch — 31J37

The genuine OEM Lennox 31J37 high pressure switch is a critical safety control that monitors refrigerant pressure on the high side of your Lennox air conditioner or heat pump. If system pressure climbs to unsafe levels — from a dirty condenser coil, blocked airflow, an overcharge, or a failing compressor — the 31J37 opens the circuit and shuts the system down to prevent catastrophic compressor damage and protect your equipment.

Common signs of a faulty high pressure switch include a system that repeatedly trips off on hot days, a unit that won't start even though the thermostat is calling for cooling, nuisance lockouts, or a compressor that runs but then cuts out shortly after. A stuck-open switch prevents operation entirely, while a stuck-closed switch removes the protection your compressor depends on.

OEM matters here because the 31J37 is calibrated to the exact cut-out and cut-in pressure thresholds Lennox specifies for your system. Using a substitute switch with the wrong trip point can leave your compressor unprotected or cause false shutdowns. The factory part guarantees correct calibration, fitment, and electrical connections for safe, reliable protection.