A.O. Smith gas water heater shows E03 and shuts down shortly after ignition attempt

Safety: Turn off power to the heater and shut off gas before servicing. Do not operate the unit with venting disconnected.

• 1. Inspect venting: Follow the PVC or metal vent pipe from the heater to the termination. Check for kinks, sags, disconnections, bird nests, leaves, or ice buildup at the termination. Clear any obstructions.
• 2. Check air intake: On direct-vent models, inspect the intake pipe and termination for blockages. Clean screens and ensure adequate clearance from snow, shrubs, or debris.
• 3. Condensate drain: If your model has a condensate trap or drain line, verify it is not clogged or frozen. Clear the trap and ensure the line slopes properly to a drain.
• 4. Pressure switch tubing: Remove the small rubber or silicone tube from the pressure switch and check for water, debris, or cracks. Blow through the tube to clear it and reattach securely.
• 5. Test pressure switch: With power off, inspect the wiring connections to the pressure switch. Tighten loose spade terminals. A technician can test continuity across the switch while the blower runs; if it does not close, the switch may be defective.

If E03 remains after clearing vents and tubing, have a professional test and replace the pressure switch or blower assembly as needed.