OEM Lennox Pressure Switch with Bracket — 19L57

The genuine OEM Lennox 19L57 pressure switch, supplied complete with its mounting bracket, is a key safety and sequencing control in your Lennox furnace. It confirms that the draft inducer is producing adequate airflow and proper venting before the control board allows the igniter and gas valve to activate — preventing the furnace from firing when combustion gases can't safely exhaust. The included bracket ensures correct positioning and a factory-accurate installation.

When a pressure switch fails or its calibration drifts, the furnace typically won't start, locks out on a pressure-switch fault code, or short-cycles. Common causes include a stuck diaphragm, a cracked switch, or a switch that won't close even when the inducer is running — all of which halt the ignition sequence as a safety measure.

The OEM 19L57 is set to the exact pressure threshold (in inches of water column) that matches your Lennox furnace's inducer and venting design. Generic switches with incorrect set points cause nuisance lockouts or bypass essential safety checks. The factory part with bracket restores correct, safe operation and eliminates guesswork on installation.