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
(failure to disconnect fan WILL cause misdiagnosis)
Disconnect connector from the fan and make safe
(failure to disconnect fan WILL cause misdiagnosis)
| 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