Set Appliance State:
Mains Power Off
Set Multimeter to AC Voltage 
CH Demand
On/Off Switch On.
Gas On
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Allow the Burner to ignite and establish.
Turn off the gas supply and allow the Boiler to Lockout.
Measure Mains Voltage across connection 2 (Red/Black wire) and connection 3 (Blue wire) on the PCB.
Turn off the gas supply and allow the Boiler to Lockout.
Measure Mains Voltage across connection 2 (Red/Black wire) and connection 3 (Blue wire) on the PCB.
Isolate as per TOPs P4
and refit as necessary