I have a Worcester 14/19 CBi, it kept locking out every two weeks or so, the thermistor sensor and the overheat thermostat have both been changed and since then it has locked out twice in two weeks.
At least I think it is still locking out. Before the repairs the lock out light flashed to indicate falme failure however the two times it has gone since the repair, the boiler demand light is steadily lit, the lock out one does not light. By turning the temperature control off and then on agin the boiler fires up straight away.
Any theories as to what the problem is here? There is never any problem getting the boiler to fire up again, there is never any trapped air in the radiators. Before the repairs the lock out happend twice after the boiler had been on an houor or so in the morning, the times since it has gone off in the afternoon.
It could be a few things, check the 3 electrodes. The two close together are the spark electrodes and the one by itself is the flame sensing electrode. Try cleaning and filing them, the flame sensing electrode is like a thermocouple. It has to sense the flame before it will bring the main burner on.
Also check the spark electrode lead and sensor electrode lead, for breaks or damage. Renew electrodes and leads if damaged. Shouldn't cost too much (probably under Â£20)
The gas pressures should also be checked. When was the boiler last serviced ?
Remember it is against the law to work on Gas appliances if you're not a CORGI registered gas installer.
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