Set Appliance State:
On/Off Switch OFF
Set Multimeter to DC Volts 
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
CH temperature switch to minimum
DHW temperature switch to maximum
Gain access to PCB (use insulation mat as necessary)
CH temperature switch to minimum
DHW temperature switch to maximum
Gain access to PCB (use insulation mat as necessary)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Turn On/Off switch to On.
Measure the voltage across connection 5 (green wire) and connection 4 (white wire) on connector X4 on the PCB.
Approximately 2.4 volts DC should be present.
Is the voltage as expected?
Measure the voltage across connection 5 (green wire) and connection 4 (white wire) on connector X4 on the PCB.
Approximately 2.4 volts DC should be present.
Is the voltage as expected?
Isolate as per TOPs P4
and refit as necessary