Fault Code 99

Fault: Your hot water system has shut down due to abnormal combustion.

Applies to: Bosch Tankless Water Heaters

Error codes are the indicators of the problems inside the water heater. When the error code appears on the Bosch heater’s LCD display, something may need to be repaired or isn’t functioning properly. Each error code has a meaning to help you understand the problem and what needs to be done to fix it.