Lennox Furnace Error Code E 272

E 272 is a soft lockout error indicating the furnace exceeded the maximum number of ignition recycles, with the last failure caused by the pressure switch opening during a heat cycle. The pressure switch monitors airflow through the venting system and opens if it detects insufficient draft pressure. This is a protective shutdown to prevent unsafe combustion. The fault will clear automatically once a heating cycle completes successfully.

The furnace has stopped firing as a safety precaution, so combustion is not occurring while the lockout is active. The code itself indicates the control board is protecting the system correctly. However, you should not attempt to force the unit to run repeatedly without diagnosing the cause, since the pressure switch is a critical safety device that confirms proper venting before allowing ignition.

Start by inspecting the vent termination and all flue pipe sections for blockages, ice, or damage. Check the pressure switch sensing hose for cracks, disconnection, or water blockage. Listen to the inducer motor during startup for unusual noise indicating bearing wear. Using a manometer connected to the pressure switch port, measure the actual operating draft pressure and compare it to the pressure switch rating to determine whether the switch, the inducer, or the venting is at fault.

E 272 is a soft lockout, meaning the control board clears it automatically once the thermostat heat call ends successfully without a pressure switch fault. You do not need to manually reset the board for the code to clear. However, if the underlying cause of the pressure switch opening is not corrected, the fault will return and the furnace will go through the same recycle sequence again.

Repair cost depends heavily on what is causing the pressure switch to open. Clearing a blocked vent or condensate trap is typically a lower-cost service call in the range of 75 to 200 dollars. Replacing a faulty pressure switch generally runs 150 to 350 dollars including parts and labor. Replacing a failed inducer motor is a more involved repair, commonly ranging from 400 to 800 dollars or more depending on the model and local labor rates.