Set Appliance State:
Gas Off
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to DC Volts 
CH temperature control to max
Disconnect connector from the fan and make safe
Disconnect connector from the fan and make safe
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage between the grey wire (pin 4) on the connector marked X20 and a suitable earth.
Approximately 5 seconds after the pump begins to run for DHW demand the voltage should increase from 0v to 17vdc or greater.
Approximately 5 seconds after the pump begins to run for DHW demand the voltage should increase from 0v to 17vdc or greater.
Isolate as per TOPs P4
and refit as necessary