Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Gain access to PCB (use Insulation Mat as required)
ON/OFF switch in the ON position
CH temp selector to MIN
DHW temp selector to MID
Set DHW flow rate at the tap to approximately 5 litres/minute
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure voltage at PCB connector X2, between pins 6 and 8 (red wires).
Allow DHW to heat, voltage should initially reach a maximum of approximately
13 volts DC then begin to reduce as the target DHW temperature is reached.
Note:
Voltage should reduce to maintain DHW at approximately 55-60° C, between 13 and 5 volts DC.