combi boiler - click

[Richard Kavanagh]

Over the last winter the boiler developed an inability to light as soon as you switch it on. The switch clicks, the gas lights and immediately you see the gas die down then go out. Then the whole process starts again. When it was cold I counted it taking 50 attempts until it lit. It does light eventually but it's getting worse as now it's having trouble sometimes when it's been on for a while.

Now we've got the cash to have it fixed does anyone have an idea of what it might be and how much it might cost? It's a Worcester 24i (if that helps anyone).

Thanks, Rich.

[Martin Pentreath]

Could it be that the flame detector is failing? It's a sensor which tries to work out whether the gas has lit properly, and if it hasn't turns it off until the boiler has another go at ignition.

[Richard Kavanagh]

That sounds exactly right thanks, I like to have an idea so that I can get some decent quotes.

Cheers! Rich.

[geoff]

In message , Richard Kavanagh writes

Flame sensing is performed on the pcb electronically, there is no sensor as such, just an electrode which connects to the flame sensing circuit on the board

The three things to check first are

1/ That the sensing electrode is actually in the flame

2/ that the flame sense lead from electrode (not the HT one) is intact

3/ that earthing is good and that you haven't done anything recently to the electrics which might have swapped live and neutral over (I had a case of this last week)

if all those check out, then barring some really strange fault, it has to be the pcb - in which case, see my website

[spamlet]

A very common question in diy fora.

Not a gas fitter you understand but, from what I have seen, the pilot gas supply is held on by the expansion of a coiled tube of one metal with a different metal inside it. The inner metal is held in the flame of the pilot light while you hold your thumb on the bypass circuit button. As the inner metal warms it expands and pushes the button on which it is bolted at the other end, and holds the pilot gas on.

The end that sits in the flame is - to my mind - deliberately made of flimsy stuff, and burns away gradually. This then turns off the pilot gas, which then turns off the main gas. Clever: but usually packs up just when you need it the most. On our old Baxi this would be about once a year. In student days we learnt that there was a certain amount of adjustment that could get the business end of a part burned sensor back in the pilot flame. Later I found that the units only cost a few quid from any gas supplies shop.

Now of course it would be highly illegal for any UKdiyer to go anywhere near such a thing, but that is most likely what has happened to your device.

Here's some pics:

(There's loads of stuff on how to replace them on the US diy sites...)

S

[geoff]

In message , spamlet writes

The following is totally wrong and should be ignored in its entirety

[Richard Kavanagh]

Thanks for the advice.