How to Fix / Troubleshooting

Safety: Turn off power and close the cold water inlet before removing any water components.

Check flow at tap: Open the hot tap fully. If flow is weak, clean tap aerators and check household water pressure.
Clean cold inlet filter: Remove and rinse the filter screen at the heater's cold water inlet.
Inspect DHW flow sensor or switch: Remove the flow sensor and ensure the turbine spins freely. On older hydraulic valve models, verify that the microswitch is actuated when water flows.
Test after cleaning: Reassemble, open inlet valve, bleed air, restore power, and open a hot tap to confirm ignition.

Note: If the unit still does not detect demand, the flow sensor/switch may need replacement.

Water heater powers on but does not ignite when a hot water tap is opened; no error code displayed.

Possible Causes