Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Remove the connector from the Low Water Pressure Switch and make safe
Refit connector X2 (blue) at the PCB if you have not already done so
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Test 1:
Measure the voltage between pin 2 at X35
on the PCB to a suitable earth point.
Voltage should be approximately 22V DC.
Test 2:
Measure the voltage between pin 4 at X35
on the PCB to a suitable earth point.
Voltage should be approximately 5V DC.