Thermador Range Error Code F73

The F73 error code on the Thermador Gaggenau Steam Oven ED-220/221 indicates that the main water inlet valve is failing to close properly after a steam cycle. The water valve in a steam oven is a solenoid-operated component that opens on command to allow water into the steam generator, then closes once the required amount of water has been admitted. When the control system detects that the valve is not seating and closing as expected, it triggers F73 to alert the technician to a potential flooding or over-steaming condition. This is a safety-critical fault because a valve stuck open can flood the oven cavity or steam generator.

The most common root causes fall into two categories: mechanical failure of the valve itself or an electrical fault in the relay board that controls the valve. On the mechanical side, mineral scale buildup from hard water is a frequent culprit, as deposits can prevent the solenoid plunger from fully seating against the valve seat. Insufficient incoming water pressure can also cause erratic valve behavior. The minimum required incoming water pressure is 16 PSI. Below this threshold, the valve may not operate with the force needed to cycle correctly.

Diagnosis should begin with verifying incoming water pressure at the supply line using a pressure gauge. If pressure meets the 16 PSI minimum, the next step is confirming that the valve solenoid is receiving proper voltage when commanded to close. If power is confirmed but the valve remains open, the valve itself is likely fouled or mechanically failed and should be replaced. If the valve appears functional but the fault persists, the relay board controlling the valve should be inspected and replaced as needed.