Set Appliance State:

Set Multimeter to AC Voltage Set meter to measure AC Volts
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Selector Switch in DHW position
Remove the pump cover
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage across terminal L (brown wire) and N (blue wire) at the pump.