Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Drain the domestic hot water circuit and remove the electrical connection to the turbine
Remove the flow sensor assembly
WARNING!
There may be residual water even when DHW inlet is turned off and water
drained, water could get in to the electrics when flow turbine is removed

Observation:

Examine the flow sensor assembly, adaptor turbine, nozzles, flow regulator
or restrictor and inlet flow filter for signs of restriction/blockage or damage.
1. Inlet flow filter
2. Flow sensor assembly
3. Adaptor turbine
4. Flow regulator
5. Nozzles