Set Appliance State:
Set Multimeter to AC Voltage 
CH Demand
Isolate Mains Power to appliance as per TOPs P4
Open the control box by removing the two securing screws and lower the access door
Draw the control board forward to allow access to the PCB
Set the boiler control switch to H position
Open the control box by removing the two securing screws and lower the access door
Draw the control board forward to allow access to the PCB
Set the boiler control switch to H position
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage across the terminals Pump L and N (neutral) connection on the main connector block.
Isolate as per TOPs P4
and refit as necessary