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zcacogp · Joined: 21 Mar 2008 Posts: 1 Location: London

Chaps,

I'm new - first post and all that, so have arrived in a state of mild desperation ...

Our Saunier Duval SD623 boiler is not firing up. The pilot light is on, but it doesn't fire up when you turn the heating on or a hot water tap on. (It's a combi.)

I have tried as much as I know how to try - both heating and hot water at once, turning the heating up to full temperature, turning the pilot light off and on again (nasty moment there - it took a LOT of time before it re-lit). If you turn the heating or hot water on, you can hear it trying to start - it makes a humming noise, as if it it is trying to light, but won't actually light up ... it feels as if it is very nearly 'there', but not quite ...

Apparently (according to Mrs zcacogp), it has been 'playing up' like this several times in the last few days - she has had the week off work, so has noticed.

Of course, it chooses now of all times to pack up - Bank Holiday weekend, snow forecast, and my folks are coming to stay ...

Any suggestions? It was doing this last night, and I thought I would try it again in the morning, which is now, and it still isn't working.

I'm not a plumber or boiler engineer, but am reasonably handy. My thoughts are that given it won't fire up with either the hot water or the heating, it is something ignition or gas related. Gas valve sticking shut, or a thermocouple given up. But this is just guesswork, and I could be a long way wrong. A friend has suggested it may be the fan, but there is a fan-like noise when you turn the heating on - a humming noise, with a slow-ish startup, which sounds to my ears like an operational fan.

Thanks, in advance, for any help you can offer ... (even if that is just recommending a good boiler chap in East London!)

Oli.

straker1966 · Joined: 06 Jan 2008 Posts: 164 Location: cambridge

the humming noise you hear could be the pump inside the boiler. you could check this by undoing the screw on the front of the pump and checking that its spinning inside. hold a rag under to collect the drips.

you dont wana get too involved with the boiler, you should really get a corgi regd engineer on it if the pump is going- could be the fan, air switch, the overheat stat might have popped, etc etc