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)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the DC voltage between pin 3 (brown)
and pin 4 (blue) on connector CN4.
The voltage measured will vary according to the system pressure (refer to the manual pressure gauge on facia) but should conform approximately to the table below;