Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Gain access to PCB (use Insulation Mat as required)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Is the LED marked I3 at the bottom left of the PCB illuminated?
Note:
Some PCBs have an additional LED marked I2 fitted.
If LED I2 is illuminated click HERE.