Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
Gain access to PCB (use Insulation Mat as required)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Reset boiler as necessary and allow boiler to complete its self check.
Activate test t1 in boiler settings.
Click here for information on setting boiler test modes.
Measure the voltage across the red wire on X3 marked 10.1
and the blue wire on X4 marked 10.2.
Mains voltage expected.
Note:
Once the test begins voltage will be present for 30 seconds.
It make take up to 10 seconds after activating t1 for the test to start.