Bosch tankless water heater shows E7 and will not operate

Safety first: Turn OFF power and gas. Do not operate the unit if you suspect vent blockage or exhaust leakage.

• Check air intake and exhaust: Inspect the intake and exhaust terminations outside the building. Remove any leaves, snow, insect nests, or other obstructions. Ensure clearances around the termination meet Bosch specifications.
• Inspect fan wheel: Remove the front cover and locate the combustion fan. Look for dust buildup, foreign objects, or signs of water intrusion. Clean the fan wheel with a soft brush and vacuum.
• Verify wiring: Check the connector from the fan to the control board. Ensure it is fully seated and that wires are not pinched or broken.
• Listen for fan operation: Restore power and call for hot water while observing the fan. If the fan does not start or makes grinding noises, the fan motor is likely failing and should be replaced.
• Professional service: Replacement of the combustion fan assembly and testing of the fan speed sensor should be performed by a qualified technician due to combustion safety considerations.