Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Turn Hot Water Tap On
Summer/Winter Switch set to Summer.
Water Thermostat to Max. (fully clockwise)
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure voltage between pin 9 (+ve) and one connection of modureg (-ve).