Set Appliance State:
Set Multimeter to AC Volts 
Isolate Mains Power to appliance as per TOPs P4
DHW Selector in Maximum (+) position
CH Selector in Minimum (-) position
ON/OFF Switch in ON position
Remove the fan plug from the PCB
DHW Selector in Maximum (+) position
CH Selector in Minimum (-) position
ON/OFF Switch in ON position
Remove the fan plug from the PCB
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Appliance will start self check sequence
Using shrouded probes measure the voltage across brown and blue labelled terminals on the PCB at X3 FAN on the rear of the lowered control box.
Expect mains voltage.
Using shrouded probes measure the voltage across brown and blue labelled terminals on the PCB at X3 FAN on the rear of the lowered control box.
Expect mains voltage.
Isolate as per TOPs P4
and refit as necessary