Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
Use Insulation Mat as required
Gain access to PCB
Selector switch set to CH/DHW position
Boiler DHW thermostat set to MAX
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Test 1: - No Demands.
Measure for AC voltage between pin 3 white (rectification voltage)
on connector CN6 to pin 3 blue (neutral) on connector CN1.
 
Expect approximately 100 Volts AC.
 
Test 2: - Turn hot water tap ON.
Allow the fan to run and ignition sequence to commence.
 
As the burner ignites, measure for AC voltage between pin 3 white (rectification voltage) on connector CN6 to pin 3 blue (neutral) on connector CN1.
 
Expect approximately 90 Volts AC.
 
Note:
The appliance may go to lockout, reset as required until the test is complete.