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
Gain access to bottom of PCB
(This may require unclipping from main bracket)
Remove the fan connector from the PCB
Note:
Ensure PCB is located safely before turning the power back ON
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the AC voltage between terminal 6 (the red wire location when plug is fitted) of the PCB fan connector and a suitable earth. The fan connection is at the bottom left hand side of the PCB.
Expect a permanent voltage of approximately 13 vac switching to approximately 130 vac as the PCB attempts to send power to the fan.
Note:
The voltage will rise and fall between 13 vac and 130 vac several times as the PCB attempts to power the fan. It is advisable to monitor the voltage over several attempts before lockout occurs.