Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to DC Volts 
CH Demand
Gain access to PCB (use Insulation Mat as required)
Selector switch in CH & HW mode
Selector switch in CH & HW mode
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage between pin 4 (light blue) at connector X401 at the PCB to a suitable earth point.
Voltage should start at approximately 6V DC, ramp up to 18V then drop back to 6V and repeat.
Voltage should start at approximately 6V DC, ramp up to 18V then drop back to 6V and repeat.
Isolate as per TOPs P4
and refit as necessary