Set Appliance State:
Gas Off
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Voltage 
Boiler On/Off Switch ON
CH Switch OFF
DHW Switch in INSTANT position
Ensure that diverter valve is cold and in its closed position (spindle fully retracted)
CH Switch OFF
DHW Switch in INSTANT position
Ensure that diverter valve is cold and in its closed position (spindle fully retracted)
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage across the brown wire (connection 12) on the switch PCB side multiplug marked A and the neutral terminal (blue wire, marked 1Mp) on the main terminal block.
Isolate as per TOPs P4
and refit as necessary