Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
CH Demand
CH temperature control to max
Set selector switch to ch/dhw
Set selector switch to ch/dhw
Gas On
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Allow the boiler to execute its ignition sequence and the burner to ignite.
Measure for AC voltage across the gas valve modulating coil terminals. Does the voltage measured operate between approximately 12 vac (max) and 7.0 vac (min) as the ch system heats up.
Measure for AC voltage across the gas valve modulating coil terminals. Does the voltage measured operate between approximately 12 vac (max) and 7.0 vac (min) as the ch system heats up.
Isolate as per TOPs P4
and refit as necessary