Set Appliance State:
Mains Power Off
Set Multimeter to DC Volts 
CH Demand
CH temperature control to maximum
DHW temperature control to minimum
CH temperature control to maximum
DHW temperature control to minimum
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Allow the burner to ignite and, after approximately 3 to 4 seconds,
measure the voltage across the connections of the modulating solenoid.
The actual voltage measured will depend on the range rating of the boiler. The boiler comes factory set to its mid range of 4.1mb for Central Heating, which should give approx. 10Vdc at the solenoid.
(Max voltage on Central Heating is approx. 16Vdc (12.5mb) and Min approx. 1Vdc (1.4mb)
Is the voltage measured between 1 and 16Vdc?
measure the voltage across the connections of the modulating solenoid.
The actual voltage measured will depend on the range rating of the boiler. The boiler comes factory set to its mid range of 4.1mb for Central Heating, which should give approx. 10Vdc at the solenoid.
(Max voltage on Central Heating is approx. 16Vdc (12.5mb) and Min approx. 1Vdc (1.4mb)
Is the voltage measured between 1 and 16Vdc?
Isolate as per TOPs P4
and refit as necessary