Set Appliance State:

Mains Power Off
Set Multimeter to AC Voltage Set meter to measure AC Volts
Turn Hot Water Tap On
Selector switch in DHW position
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:


Allow fan to run and ignition sequence to commence.
Test 1:
Measure the voltage across brown wire (marked GV) on connector X5
and neutral (marked N) on connector X1 on PCB.
Test 2:
Repeat test across black wire on connector X5 and neutral (marked N) on connector X1 on PCB.