Set Appliance State:
Set Boiler Control Thermostat to MAX position
Set Multimeter to AC Volts 
CH Demand
Isolate Mains Power to appliance as per TOPs P4
Gain access to PCB
Use insulation mat where necessary
External controls calling for heat
Gain access to PCB
Use insulation mat where necessary
External controls calling for heat
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Allow fan to run
Measure the voltage across the connection P (pump live) and the connection marked PN (pump neutral)) on the main connector in control box.
Expected voltage 230 volts AC (mains voltage)
Measure the voltage across the connection P (pump live) and the connection marked PN (pump neutral)) on the main connector in control box.
Expected voltage 230 volts AC (mains voltage)
Isolate as per TOPs P4
and refit as necessary