Set Appliance State:
On/Off Switch OFF
Set Multimeter to DC Volts 
Isolate Mains Power to appliance as per TOPs P4
Gas On
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Appliance On/Off control set to On position.
Measure the voltage between the green wire and white wire at the flow switch inline connector. Voltage should be 0 volts DC.
Turn hot water tap On.
Repeat test. Voltage should be approximately 2.5 volts DC.
Note: Do not disconnect inline connector.
Measure the voltage between the green wire and white wire at the flow switch inline connector. Voltage should be 0 volts DC.
Turn hot water tap On.
Repeat test. Voltage should be approximately 2.5 volts DC.
Note: Do not disconnect inline connector.
Isolate as per TOPs P4
and refit as necessary