Alpha 240P combi boiler - Pilot light problems

[tcm]

I have 2 problems. The first one is when I press down the gas valve control, the fan is at full speed, but after 10s, the pilot light does not come on. However, if I remove the combustion chamber front cover (i.e. the burners can be seen), and repeat the above procedure, the pilot light comes on and stays on, even if I release the gas valve control.

The second problem is that when I turn off DHW, the burner flames go out, as expected, but the pilot light goes out too. This is the same problem when CH is turned off.

I have phoned Alpha boilers and they advised that the second problem is due to the “flame sensor moved”. However, I have measured the gap between the electrode tip and the top of the pilot burner, which is 5mm. The service manual states the same figure. The electrode tip has already been cleaned but the problem still exists.

Does the electrode also provide flame sensing? Can anyone shine some light on these problems? Thank you in advance.

 

[tcm]

In the second problem, when the pilot light went out and after a few seconds, I heard a click sound and saw the gas valve control pushed out automatically. I think the gas valve shutdown due to no pilot flame sensed.

 

[Paul Barker]

The ignition microswitch paddle may need a slight bend to make it work when operated by the plastic knob on front.

If the pilot goes out you are looking at pilot jet cleaning or renewal, thermocouple, gas valve.