Set Appliance State:
Mains Reset Switch OFF
Set Multimeter to DC Volts 
Isolate Mains Power to appliance as per TOPs P4
Ensure the boiler is cool so that there is demand for preheat
Set DHW temperature selector to ECO
Ensure the boiler is cool so that there is demand for preheat
Set DHW temperature selector to ECO
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Mains reset switch ON.
Measure voltage across pin 1 of fan connector and a suitable earth point.
Expected voltage approximately 27 - 38 volts DC.
Note.
1. Ensure a good electrical connection is made at fan connector or misdiagnosis will occur.
2. Harness colours may change but test points will remain the same.
Measure voltage across pin 1 of fan connector and a suitable earth point.
Expected voltage approximately 27 - 38 volts DC.
Note.
1. Ensure a good electrical connection is made at fan connector or misdiagnosis will occur.
2. Harness colours may change but test points will remain the same.
 in situ 2.gif)
Isolate as per TOPs P4
and refit as necessary