Set Appliance State:
Mains Power Off
Set Multimeter to AC Volts 
CH Demand
Turn Hot Water Tap On
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Reset appliance as necessary.
Approximately 6 seconds after mains power is turned on, measure the voltage between pins 4 and 5 (blue and brown wires) at connector J3 on the control PCB.
Mains voltage expected.
Approximately 6 seconds after mains power is turned on, measure the voltage between pins 4 and 5 (blue and brown wires) at connector J3 on the control PCB.
Mains voltage expected.
Isolate as per TOPs P4
and refit as necessary