boiler gas valve replacement

I finally got a plumber round to look at my failing gas boiler. Basically system fires up, then when it reaches required temperature it cuts out - pilot and everything. There is nothing wrong with pilot, thermocouple etc and I checked the circuit boards.
Just looking at it, he told me that the fault was the gas valve which would need replacing. Of course, like all his brethren, he is too busy to do this in the next month or so, but he said it is something I could do myself.
So, is he likely to be correct in his diagnosis? Is he right to suggest that this job could be done by a competent DIYer?
thanks in advance for any response
Stony
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Firstly, if he is a plumber then his experience and knowledge of gas controls is probably very limited. People make the mistake of thinking plumbers are experts at heating. they are not. they are good at drains and gutters. The people to go to should be heating engineers. A company that only does heating - not heating and plumbing.
The wires generally just plug into the valve (make a note of what goes where). The valve is just a screw in screw out job. Any screwed thread put on jointing compound.
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Stoney wrote:

Um... Firstly whilst there is a small chance that the probelm is the gas valve something like this sounds more like an over enthusiastic overheat cutout or a loose connection to same.
If changing the thermocouple is 1 out of 10 on a scale of difficulty then the gas valve is like to be 5-9 on the same scale. This is a gas carrying part and really is in the league of 'if you have to ask about it then you probably are not competant to work on it'.
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On Mon, 13 Oct 2003 13:51:29 +0100, "Stoney"

Just had a gas valve replaced on my Potterton boiler, which was done by Potterton's own maintenance company. The engineer changed the PCB first (although this was not required IMO), then ran through the simple diagnostic checks which led him to conclude, as I had, that the gas valve was faulty. He then made a phone call, popped out, came back with the valve and fitted it.
The actual fitting of the valve is fairly simple, just a few screws, but you obviously have to make sure that everything is tight and leak-free. However, the engineer then used some kind of flow meter to set up the new valve, which I would not have been able to do.
This was all done for a fixed fee, which was nice :-)
Anyway, having said that, I don't see that this is the gas valve, as it sounds like it is working every time to actually light the burner (mine was not lighting). The fact that it goes out when hotter makes me think it is a sensor issue, as others have suggested.
-- Colin Swan
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Probably took it to study what we do to pcbs.

Boilers usually go down because of a single failure, i.e. it's statistically very unlikely that two faults occur at the same time unless, of course, one fault actually causes another.

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I thought he might take it, but he didn't so I now have a spare PCB, and a broken gas valve.

I got the feeling that they change the PCB as a matter of course, regardless of the actual problem :-)
-- Colin Swan
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Let's face it, that would probably cure 90% of the problems without them having to look further
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wrote:

May they should have all these board in their top pockets in case.
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