Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the cover from the valve
Remove the synchron motor from the valve

Measurement:

CAUTION: If the motor has jammed it could be very hot, take care when removing.
Measure the resistance of the synchron motor.
Expect a reading of between 2 - 3K Ohm