Set Appliance State:

Mains Power Off
Gas Off
Turn Hot Water Tap On
Mode Selector Switch to DHW position.
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

NOTE: Remove boiler flow microswitch cover (depress single rear plastic clip) to view.
Does the Boiler Flow Switch spindle operate the Boiler Flow Microswitch?