Set Appliance State:

Mains Power Off
Set Multimeter to AC Voltage Set meter to measure AC Volts
CH Demand
CH/HW switch in CH position
Ensure boiler is not in Pre-heat mode
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Is there any resistance felt when manually moving the manual operation lever located on the diverter valve across to its open position?