Control displays 'Blocked Vent', 'Vent Block', or similar; inducer may run but burner will not fire.

Safety first: Turn off power and gas. Carbon monoxide risk is high with vent blockages.

• Inspect exterior terminations: Go outside and locate the vent and combustion air intake terminations. Clear away snow, ice, leaves, or other obstructions. Maintain required clearances from shrubs and structures.
• Check vent slope and support: Inside, visually inspect accessible vent piping. Ensure it is properly supported and sloped per Weil-McLain instructions (usually back toward the appliance for condensate drain).
• Look for signs of water accumulation: Stains or dripping at joints can indicate condensate pooling due to improper slope or blockage.
• Reset and test: After clearing obstructions, reset the control and observe operation. If the Blocked Vent fault returns, have a technician perform a full vent system inspection.