Set Appliance State:

Mains Power Off
Set Multimeter to AC Volts Set meter to measure AC Volts
Selector switch to heating
CH temperature selector to maximum
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage across the brown and blue wires on the diverter valve motor. Voltage should be about 0V.
Apply CH demand.
Voltage should rise to 240V.