Bosch water heater displays A2; unit may continue to run but with limited performance

Safety first: Turn OFF power and gas before removing covers. Do not ignore combustion-related warnings.

• Check vent terminations: Inspect intake and exhaust terminations for partial blockages such as screens clogged with lint, insect nests, or snow buildup. Clear obstructions.
• Verify venting design: Compare your vent length, number of elbows, and pipe size to the Bosch installation manual. If your installation exceeds limits, consult a professional to correct it.
• Clean combustion fan: Remove the front cover and gently clean dust from the fan wheel and housing. Ensure the fan spins freely by hand.
• Monitor operation: Restore power and run hot water while listening for abnormal fan noises. If the fan is slow to start or noisy, it may be failing and should be replaced.
• Professional service: Persistent A2 warnings indicate a combustion air problem that should be evaluated by a qualified technician with proper test equipment.