Boiler shows E3 and will not start; inducer fan may not run or stops quickly.

Safety first: Turn off power and gas. Working on venting and combustion air systems should be done carefully to avoid carbon monoxide hazards.

• Step 1 – Inspect vent and intake: Go outside and check the boiler’s exhaust and intake terminations. Remove any snow, leaves, nests, or debris blocking the openings. Ensure vent screens are clear.
• Step 2 – Check pressure tubing: Remove the front panel and locate the air pressure switch and its rubber or silicone tubing. Inspect for cracks, kinks, water accumulation, or disconnections. Reattach or replace tubing as needed.
• Step 3 – Test pressure switch operation: With power OFF, gently tap the pressure switch body; sometimes a stuck diaphragm can free up. Ensure the electrical connectors are tight. Do not blow into the switch; this can damage it.
• Step 4 – Verify inducer operation: Restore power and call for heat. Observe whether the inducer motor starts and runs smoothly. If the inducer hums, is noisy, or does not start, it may be failing and should be replaced.
• Step 5 – Replace pressure switch if needed: If the venting is clear and inducer runs but E3 persists, the pressure switch may be defective. Replace with the exact Bradford White-specified switch.

Warning: Never operate the boiler with the pressure switch bypassed; this defeats a critical safety device.