Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to DC Volts 
Gain access to PCB (use Insulation Mat as required)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure the DC voltage between pin 4 on connector X20 and an earth (use the copper pipe to the gas valve as earth).
Expect approximately 22 Vdc.
Is the voltage as expected?
Expect approximately 22 Vdc.
Is the voltage as expected?
Isolate as per TOPs P4
and refit as necessary