Set Appliance State:
Set Multimeter to AC Volts 
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Gain access to PCB, use isolation mat as required
Gain access to PCB, use isolation mat as required
Gas On
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Appliance On/Off control set to ON position.
Measure the voltage at connector ST1 centre pin (white wire)
and a suitable neutral.
Note:
If voltage is only present briefly then select "mains voltage absent"
Measure the voltage at connector ST1 centre pin (white wire)
and a suitable neutral.
Note:
If voltage is only present briefly then select "mains voltage absent"
Isolate as per TOPs P4
and refit as necessary