Set Appliance State:
Mains Power Off
Set Multimeter to AC Volts 
Turn Hot Water Tap On
Boiler Operating Switch / Programmer set to WATER only
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage across connection FL (Brown wire) and connection FN (Blue wire) on connector CN5 on the sequence control PCB.
Note:
On some models sequence control PCB may have only numbered connections in which case FL will be connection 14 and FN will be connection 15.
Note:
On some models sequence control PCB may have only numbered connections in which case FL will be connection 14 and FN will be connection 15.
Isolate as per TOPs P4
and refit as necessary