Set Appliance State:
Set Multimeter to AC Voltage 
CH Demand
Isolate Mains Power to appliance as per TOPs P4
CH/HW switch in CH position
Boiler switch in On position
Ensure boiler not in Pre-Heat mode
Gain access to PCB (use insulation mat as required)
Ensure base of PCB 27 is insulated and not in contact boiler as shorting will occur
CH/HW switch in CH position
Boiler switch in On position
Ensure boiler not in Pre-Heat mode
Gain access to PCB (use insulation mat as required)
Ensure base of PCB 27 is insulated and not in contact boiler as shorting will occur
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage across the connections on the connector
marked CON 2 gas valve 3 (violet wires) on PCB 27.
marked CON 2 gas valve 3 (violet wires) on PCB 27.
Isolate as per TOPs P4
and refit as necessary