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The genuine OEM Lennox 33W19 dual pressure switch assembly monitors combustion airflow and venting draft, confirming that the draft inducer has established proper pressure before the furnace is allowed to ignite. Its two switches verify draft at multiple firing conditions, acting as a key safety interlock in compatible Lennox gas furnaces.
Common failure symptoms: A faulty pressure switch commonly causes no-heat conditions, ignition lockouts, and blinking fault codes on the control board. You may see the furnace attempt to start and then shut down, cycle repeatedly, or refuse to fire because the switch is stuck open, stuck closed, or reading incorrect pressure.
Why OEM matters: The 33W19 is calibrated to the precise pressure setpoints (in inches of water column) your Lennox furnace requires. An incorrectly rated aftermarket switch can allow the furnace to fire without safe venting or nuisance-trip on every cycle. Genuine OEM guarantees the correct trip points and connections, preserving both safe combustion and reliable heating.