Set Appliance State:
Mains Power Off
Set Multimeter to DC Volts 
DHW Demand
On/Off Switch ON
Gas On
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Allow ignition sequence to commence.
Measure the DC voltage across the Black and Blue leads on the gas valve during the sparking stage of the ignition cycle.
Expected voltage should be approximately 150 volts DC.
Measure the DC voltage across the Black and Blue leads on the gas valve during the sparking stage of the ignition cycle.
Expected voltage should be approximately 150 volts DC.
Isolate as per TOPs P4
and refit as necessary