Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
CH Demand
Gain access to PCB (use Insulation Mat as required)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
As boiler has been switched off it may light for a while, wait until
fault occurs (burner shuts off early) before continuing test.
Measure the voltage between the black wire marked "GV1" and
the blue wire marked "N" at the rightmost plug on the PCB.
Is mains voltage still present?
fault occurs (burner shuts off early) before continuing test.
Measure the voltage between the black wire marked "GV1" and
the blue wire marked "N" at the rightmost plug on the PCB.
Is mains voltage still present?
Isolate as per TOPs P4
and refit as necessary