OEM Lennox Draft Inducer Blower Motor — 21L91

The genuine OEM Lennox 21L91 draft inducer blower motor pulls combustion gases through the heat exchanger and pushes them safely out the flue. It runs at the start of each heating cycle to establish proper draft, closing the pressure switch that proves safe venting before the gas valve and burners are allowed to fire.

Common failure symptoms: A worn or failing 21L91 inducer motor often produces loud humming, rattling, or grinding from failing bearings, a motor that hums but won't spin, or intermittent no-heat calls. Because the pressure switch depends on this motor, a weak inducer commonly triggers a pressure-switch fault, ignition lockout, or a furnace that never begins the ignition sequence.

Why OEM matters: Lennox specifies the 21L91 for a precise airflow rate, CFM, and RPM that its pressure switch and combustion design require. An underpowered aftermarket motor may not draw enough draft to reliably close the pressure switch, causing nuisance lockouts and poor combustion. The OEM 21L91 guarantees correct mounting, matched airflow, and safe, code-compliant venting on compatible Lennox, Armstrong, and Ducane furnaces.