Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Turn Hot Water Tap On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Reset appliance as necessary.
Measure the voltage between pin 1 (blue) and pin 3 (black) at X3 on the PCB.
At 40 second intervals 24V DC should be measured
for 4 seconds as power is sent to the gas valve, this
will be repeated 5 times until lockout occurs.
Is the voltage measured as expected?
Notes:
1. Timings / voltages quoted are approximate.
2. Reset appliance and repeat test as necessary until outcome is determined.
3. Pins 2 and 3 are very close together, ensure test is carried out on pin 3.