Set Appliance State:

Mains Power Off
Set Multimeter to DC Volts Set meter to measure DC Volts
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure for DC voltage across the red lead (pressure sensor connector) and
terminal 2 (blue) main terminal block, this voltage will vary depending on
the system pressure.
Expected voltage approximately 1.0 - 1.5 Vdc (1 - 1.5 bar).
System pressureVoltage dc
1 bar 1.0
2 bar2.0
3 bar3.0

Note.
Terminal 1 of main terminal block is the top connection when facing appliance front.