Boiler display shows A03 and will not start; fan may not run or runs briefly then stops.

Safety first: Turn OFF power to the boiler. Do not operate the unit if you suspect a blocked vent or intake, as this can cause carbon monoxide buildup.

Steps:

• 1. Inspect vent and air intake: From outside, check the Raypak boiler vent and combustion air intake terminations. Remove leaves, nests, snow, or debris. Ensure vent screens are clear.
• 2. Check pressure tubing: Open the boiler cabinet and locate the air pressure switch and its silicone tubing. Make sure the tubing is firmly connected at both ends, not kinked, and free of water or condensation. Replace brittle or cracked tubing.
• 3. Test the combustion blower: With power restored, listen for the inducer fan starting when there is a call for heat. If the fan does not run, or is noisy and slow, shut power off and inspect the blower wheel for obstructions. A failed blower motor will require replacement.
• 4. Inspect the air pressure switch: With power off, check that the switch mounting and wiring are secure. If you have a multimeter and training, you can verify continuity when the inducer is running (performed by a technician). If the switch does not close when proper draft is present, it is likely defective.
• 5. Reset and test: After clearing any blockages and verifying tubing and blower operation, reset the control and call for heat. If A03 persists, the air pressure switch or control board may need replacement by a qualified technician.