Boiler locks out with E03, no ignition, inducer may run briefly then stop

Safety: Turn off power to the boiler. Do not operate the boiler with a known vent blockage; risk of carbon monoxide.

Diagnostic steps:

• 1. Inspect vent and intake: From the outside termination, check that PVC vent and intake pipes are free of leaves, nests, snow, or ice. Clear any obstructions.
• 2. Check condensate drain: On condensing Slant/Fin boilers, verify the condensate trap and drain line are not clogged. Remove the trap, flush with water, and reassemble, ensuring proper slope on the drain line.
• 3. Examine pressure switch tubing: Remove the silicone tubing from the air pressure switch and inducer ports. Look for water, debris, or cracks. Clean or replace tubing as needed.
• 4. Test pressure switch operation: With power off, check that the switch terminals are not corroded. A technician can test continuity across the switch while the inducer runs to confirm it closes properly.
• 5. Inducer motor check: Listen for the inducer fan starting when there is a call for heat. If it hums, squeals, or fails to start, the inducer assembly may be failing and should be replaced.

Professional help: If E03 persists after clearing venting and condensate and verifying tubing, contact a qualified technician to test the pressure switch and inducer motor under operating conditions.