Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
CH Demand
Preheat OFF
Boiler mains switch On
Ensure External Controls are calling for heat
Gain access to PCB (use insulation mat as required)
Boiler mains switch On
Ensure External Controls are calling for heat
Gain access to PCB (use insulation mat as required)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Allow the ignition sequence to commence and burner to ignite.
Measure the voltage across pin 2 (black) and pin 3 (blue) at connector X1D (4 way, 4th from left) on the PCB.
Measure the voltage across pin 2 (black) and pin 3 (blue) at connector X1D (4 way, 4th from left) on the PCB.
Isolate as per TOPs P4
and refit as necessary