Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove connector X1 from the PCB
Measurement:
Test 1:
Measure the resistance between the pins 3 and 4 on connector X1.
Resistance should be approximately 48 ohms.
Test 2:
Measure the resistance between pin 3 on connector
X1 to a suitable earth point.
Resistance should be greater than 1M Ohm (or O.L)
Are the resistances as expected?
Measure the resistance between the pins 3 and 4 on connector X1.
Resistance should be approximately 48 ohms.
Test 2:
Measure the resistance between pin 3 on connector
X1 to a suitable earth point.
Resistance should be greater than 1M Ohm (or O.L)
Are the resistances as expected?
Isolate as per TOPs P4
and refit as necessary