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.
HW Thermostat on Max.
Connect meter across modureg coil.
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Reduce flow from HW tap for approx one min.
Turn thermostat anticlockwise until click is heard.
Measure voltage across modureg and observe burner.