Set Appliance State:

Mains Power Off
Set Multimeter to DC Volts Set meter to measure DC Volts
DHW Demand
DHW Selector in Maximum (+) position
CH Selector in Minimum (-) position
ON/OFF Switch in ON position
Press the reset button to reset any lockout condition.
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the DC voltage between the black wire of the fan connection to each wire of the ignition PCB low voltage connection. The readings should match approximately the table below.
WIREVOLTAGE (DC)
White0v
Brown 5v
Blue5v
Gray0v