Boiler intermittently shuts down with error 34, often in windy conditions or when venting is marginal.

Safety first: Turn off power and gas. Combustion components can be hot and flue gases hazardous.

• Inspect vent terminations: Ensure intake and exhaust terminations are correctly spaced and oriented to prevent flue gas recirculation.
• Locate combustion air sensor: This thermistor is typically mounted near the air intake or in the combustion chamber area.
• Check sensor and wiring: Confirm the sensor is secure and wiring is intact with no signs of heat damage or moisture.
• Reset and monitor: After reseating connectors, restore power and reset the boiler. Observe operation, especially during windy conditions.
• Professional evaluation: Persistent error 34 may require replacement of the combustion air sensor or control PCB and a full combustion analysis by a technician.