OEM Lennox Pressure Switch — 33J88

The genuine OEM Lennox 33J88 pressure switch is a combustion safety control that verifies adequate venting and draft before your Lennox furnace fires. By monitoring the negative pressure generated by the draft-inducer motor, the 33J88 ensures the burner only ignites when the flue path is clear and airflow is correct, guarding against the spillage of combustion gases into the home.

Common failure symptoms: When the 33J88 fails or detects a venting issue, you may see a furnace that won't start, short-cycles on ignition, runs the inducer without progressing to heat, or reports a pressure-switch/lockout code on the control board. Root causes include a switch stuck open or closed, a pinched or condensate-filled sensing hose, or a restricted vent or drain.

Why OEM matters: Each pressure switch is calibrated to a precise trip pressure suited to the furnace's venting and altitude design. The factory Lennox 33J88 matches that exact set point and connector, delivering dependable safety shutoff and correct ignition sequencing. Substituting a switch with a different calibration can cause nuisance lockouts or, worse, allow unsafe operation — which is why the OEM part is the right choice for your Lennox system.