Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to DC Volts 
Gain access to PCB (use Insulation Mat as required)
DHW temperature selector to Max
DHW temperature selector to Max
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage between the grey wires on connector X4 at the PCB.
Shortly after the pump begins to run the voltage
should drop from 26V to approximately 0V DC.
Continue to monitor the voltage until the boiler cuts out.
Does the voltage change back to 26VDC indicating the
flow switch has cut out or does the voltage remain at 0V?
Shortly after the pump begins to run the voltage
should drop from 26V to approximately 0V DC.
Continue to monitor the voltage until the boiler cuts out.
Does the voltage change back to 26VDC indicating the
flow switch has cut out or does the voltage remain at 0V?
Isolate as per TOPs P4
and refit as necessary