Vokera water heater shows code 04, no hot water, appliance does not attempt to ignite when tap is opened

Safety first: Turn off power and close the cold water isolation valve before removing any water connections. Risk of scalding and leaks.

Basic user checks:

• Check water supply: Ensure the main stopcock is open and that cold water pressure at other taps is normal.
• Clean tap aerators and shower heads: Heavy limescale can reduce flow below the minimum required to trigger the heater.
• Try opening a different hot tap fully to see if the heater responds.

Technician-level steps:

• Isolate and remove the DHW inlet filter on the cold inlet to the heater; clean any debris or scale.
• Test the DHW flow switch or turbine flow sensor for correct operation and replace if sticking or electrically open-circuit.
• Inspect wiring from the flow sensor to the PCB for loose connectors or damage.

If you are not experienced with plumbing and electrics, contact a qualified engineer to service the flow sensor assembly.