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 component 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 inlet filter, flow regulator and nozzles for signs of damage or blockage.