Set Appliance State:
Mains Power Off
Set Multimeter to AC Volts 
CH Demand
Boiler On/Off Switch On
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Allow fan to run and ignition sequence to commence.
Measure the voltage at connector CN1 third from bottom (red wire) on control PCB and a suitable neutral.
Once the burner has lit voltage should increase from approximately 0V AC to mains voltage.
Measure the voltage at connector CN1 third from bottom (red wire) on control PCB and a suitable neutral.
Once the burner has lit voltage should increase from approximately 0V AC to mains voltage.
Isolate as per TOPs P4
and refit as necessary