Set Appliance State:
Set Multimeter to DC Volts 
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Remove connectors from main gas valve solenoids (brown leads and violet leads)
Remove connectors from main gas valve solenoids (brown leads and violet leads)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Test 1: Allow boiler to commence its ignition sequence, when sparking starts at the electrodes
test for approximately 22 volts DC across the disconnected gas valve plug.
Test 2: Repeat test on the other disconnected gas valve plug.
Note 1: It is important that the measurement is not taken until sparking has commenced.
If multimeter probes are placed on the connections before sparking commences boiler may go to lockout.
Note 2: Lockout will occur after ignition has been sparking for approximately 10 seconds, boiler may have to be reset between tests.
test for approximately 22 volts DC across the disconnected gas valve plug.
Test 2: Repeat test on the other disconnected gas valve plug.
Note 1: It is important that the measurement is not taken until sparking has commenced.
If multimeter probes are placed on the connections before sparking commences boiler may go to lockout.
Note 2: Lockout will occur after ignition has been sparking for approximately 10 seconds, boiler may have to be reset between tests.
Isolate as per TOPs P4
and refit as necessary