Baxi System Boiler - flame light flashes after 2 hours of running

[kmillar]

I have a Baxi System 30/65 Boiler which is about 2 years old exactly.

In the past few days it has started mis-behaving. It will run perfectly for about 1 to 2 hours, then it shutsdown and the Flame light (first red LED) flashes on and off.

If I turn the dial to Reset and back it will run again for another 1 or 2 hours.

I had a look in the service manual and it says check condition/ position of flame sensor, which I did. Condition wise it looks OK, not pitted or badly burned or anything. Can't comment on the position, it appears to have the tip in the flame while it is running, but I don't know what position it is supposed to be in. Can't imagine it has moved.

What could be causing this? Any ideas?

[Ed Sirett]

These are the really awkward jobs. Try checking the flame sense lead for a problem?

[kmillar]

Hi and thanks for the reply. I took your advice and checked the flame sensor lead. Could not detect any problems. I disconnected everything fromt the PCB, removed the PCB and carefully checked it for dry joints etc - nothing found.

However here's the thing. I'd had the temperature dial at about 75%. I turned the dial right round to max, and the problem has gone away.

I wonder if this then points to the gas modulator valve? If I'm correct the system has the ability to modulate the flame between two pressures - looks like the 'min' pressure might be too low, causing the flame to go out. I think when the temp dial is at max it must not be modulating the flame.

That's my theory anyway. Might be totally wrong.

-Kenny

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