Navien furnace shows E010 and shuts down, fan may run at high speed

Safety: Turn off power and gas before servicing. Combustion air and venting issues can cause unsafe operation.

• Inspect vent and intake: From the exterior terminations, check for ice, snow, insect screens, or debris blocking the PVC pipes. Clear obstructions and ensure terminations are not recessed or too close to grade.
• Check pressure switch tubing: Open the front cover and locate the air pressure switch and its silicone tubes connected to the fan housing or vent collar. Ensure tubes are not kinked, cracked, or filled with condensate. Replace damaged tubing and clear any water by gently blowing through the tube (with power off).
• Test the pressure switch: With power off, disconnect the wiring from the pressure switch and check continuity across the contacts while gently applying suction to the tube. The switch should click and show continuity. If it does not operate smoothly, replace the pressure switch with a Navien OEM part.
• Check combustion fan: Spin the fan wheel by hand to ensure it turns freely and is not obstructed. If the fan is noisy, seized, or does not run when the unit calls for heat, the fan motor may be defective and should be replaced.
• Reset and verify: After corrections, restore power and gas, reset the unit, and observe startup. Persistent E010 indicates a possible control board fault or deeper venting design issue that should be evaluated by a Navien-trained technician.