Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the 3 wire connector from the fan

Measurement:

Test 1:
Measure the resistance between the 2 outer terminals.
Expected resistance 1 MOhm or greater.
(O.L is acceptable because it is greater than 1 MOhm)
Test 2:
Measure the resistance between one of the outer terminals and the middle terminal (it does not matter which outer terminal).
Expected resistance 1 MOhm or greater.
(O.L is acceptable because it is greater than 1 MOhm)
Are the resistances as expected?
Note:
If the right hand side panel can be removed then the test can be carried out with the fan in situ, otherwise it may have to be removed.