Combi Boiler Ravenheat CSI 85A

Hi,
I'm passing this request along for a friend, so please forgive any ignorance or mistakes on my part. The problem is with a Ravenheat CSI 85A combi boiler... it won't light (duh!).
The unit was self-installed, and has worked without problems for the last few years. A week or so ago, the unit would no longer light reliably. Turning on the hot water tap became a pot luck affair. If you left it running for 20-30m, you might get hot water eventually. A visual inspection of the boiler during this time showed the boiler lighting for a few seconds, but then turning off again. It would, on occasion, decide to light properly and deliver hot water untill the tap was turned off again.
Since then the problem has gotten worse. Now the fan works, but the pilot light will not light and the pump will not run. The fan only works intermittently though.. it will come on for a few minutes and then turn off for a few minutes.
The ignition board has been replaced, but it made no difference.
Does anyone have any advice on what may be wrong?
Thanks in advance.
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............
So the pilot light will not light? It is the pilot light that lights the main gas burner, so it sounds like a pilot fault. Screwfix, and most decent plumbers merchants (I've seen them in B+Q too) sell a universal pilot light thermocouple kit for around £5. When my pilot wouldnt stay alight, I changed the thermocouple, and all was fine again. Alan.
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The CSI 85A is a condensing boiler with electronic ignition
The reply above (for a pp boiler) is completely wrong
The problem could lie anywhere from not sensing the fan through a faulty pcb to a valve solenoid
The description is so vague that it isn't really possible to make more of a diagnosis - get a man in
--
geoff

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On Oct 17, 9:58 pm, snipped-for-privacy@gmail.com wrote:

I had a similar problem with my son's Ravenheat boiler.
Ravenheat have a good website with manuals for their boilers and fault finding charts.
When the fan starts a sensor detects that there is a pressure difference between the flue and the boiler.
Two possible faults here 1. The sensor is not working or its tubes are blocked or leaking: or 2. The boiler casing is not properly sealed (in my son's case the casing seal round the flue had come loose)
If the pressure sensor is working then you should hear the igniter clicking. If it clicks but the pilot does not light, then there is a problem with the gas circuit and I suggest you get in a professional.
If there is no clicking then change the igniter spark plug and check the lead to the plug.
Hope this helps a bit.
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