Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
Turn Hot Water Tap On
Gain access to PCB (use Insulation Mat as required)
Remove 1x lead from overheat stat & make safe
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Fault code ALL 07 will be displayed during test, this will not affect test results
Test 1.
Measure for AC voltage across pins 66 & 67 of connector CN13.
Expected voltage, mains voltage.
Test 2.
Measure for AC voltage across pins 62 & 63 of connector CN15.
Expected voltage approximately 140 Vac.