Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
Turn Hot Water Tap On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Reset appliance as required (press and hold the reset button until the chimney sweep button led flashes rapidly, then release the reset button)
Allow the pump purge to complete and ignition sequence to commence.
Measure for AC voltage across the brown and blue leads at the gas valve connector, approximately 8 seconds from the fan starting, mains voltage should be present for approximately 4 seconds to open the gas valve, this will occur five times before ignition lockout occurs.
Note:
Reset appliance as required until test complete.