Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
DHW Demand
Gain access to PCB (use Insulation Mat as required)
Selector switch in HW mode
Selector switch in HW mode
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage between pin 5 (blue) and
pin 7 (brown) wires of X3 on the main PCB.
Mains voltage should be present.
pin 7 (brown) wires of X3 on the main PCB.
Mains voltage should be present.
Isolate as per TOPs P4
and refit as necessary