Set Appliance State:
Mains Power Off
On/Off Switch OFF
Set Multimeter to AC Volts 
CH Demand
External controls calling for heat
CH temperature switch to maximum
DHW temperature switch to minimum
CH temperature switch to maximum
DHW temperature switch to minimum
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Turn On/Off switch to On.
Allow fan to run.
Measure the voltage across connection 10 (brown wire) on connector X6 and connection 2 (blue wire) on connector X1 on the PCB.
Mains voltage expected.
Note:
Some voltage will be present before the fan runs, take the reading once the fan is running as described above.
Allow fan to run.
Measure the voltage across connection 10 (brown wire) on connector X6 and connection 2 (blue wire) on connector X1 on the PCB.
Mains voltage expected.
Note:
Some voltage will be present before the fan runs, take the reading once the fan is running as described above.
Isolate as per TOPs P4
and refit as necessary