Set Appliance State:
Mains Power Off
Set Multimeter to DC Volts 
DHW temperature selector to 0 position
CH temperature selector to 0 position
CH temperature selector to 0 position
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
All heating controls calling.
Measure voltage across the clock 24 volt output terminal and the main neutral on the PCB. Expected voltage between 22 and 40 volts DC.
Note:
The clock 24 volt output is the second connection down from the top (purple lead) of the five connection plug to the right of the fuse marked T125 amp on the PCB.
Measure voltage across the clock 24 volt output terminal and the main neutral on the PCB. Expected voltage between 22 and 40 volts DC.
Note:
The clock 24 volt output is the second connection down from the top (purple lead) of the five connection plug to the right of the fuse marked T125 amp on the PCB.
Isolate as per TOPs P4
and refit as necessary