ravenheat csi85 sparks pilot lights 1 sec then goes out!

10 Jan 2010
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United Kingdom
I recently fixed my friends Ravenheat CSI 85 boiler by replacing the CH thermistor. It was fine for a fortnight then it developed a new fault. I think the issue is with the gas valve - but this is an expensive part and I would like some opinions before I buying it.

Call for central heating
Pump runs
Fan runs
Ignitor sparks
Pilot lights for 1 second then goes out

Addition info:-
Pressure at 1.5 bar
Both thermistors at around 20K ohms cold

I have back probed the ignition boards connection to the main gas valve, when the pilot lights the multimeter flicks up to around 80 volts AC. I assume it doesn't reach the full 230 because it is connected and the valve is soaking up the other 150.

To prove my theory about the gas valve I was going to connect the Gas valve directly to the mains and see if I get gas in the combustion chamber. Good idea??

How does the boiler 'know' the pilot is lit, I can't see any thermocouple I read something about a the ignition flame detector but I haven't a clue - can someone explain?

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get an rgi who does have a clue mate. what your doing is illegal and not to mention dangerous.
I got an rgi out for the initial problem, when it was not even attempting to light (just pump running). He told me the issue was the ignition board and the air pressure switch. He quoted £250 for the parts plus fitting. It was the CH thermistor and cost £6.50 from ebay.

When I said haven't a clue I just meant I don't know how the flame detection works with no theromocouple- can you explain?

I wanted to prove it was the gas valve, buy one and then get it fitted by an rgi so it can be checked for tightness, pressure -without getting seen off.

What is the point of the forum if the response is simply 'phone the man'?
the spark electrode also senses the flame, these need a good sized pilot flame otherwise will get these problems.

so possibly just a pilot injector needed.........

RGI territory, not DIY job......

let us know outcome please
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On this particular model the ignition detection and Spark are done by the same lead. 4565TF honeywell control board.
Sorry just realised you knew that. No I haven't. I assumed as it sparked the lead is good - although I realise the spark is high voltage and the signal is very low voltage. Is this the likely cause?
From my experience with the csi 85 I would suggest an issue with the balancing of air.
Why would you assume that a gas valve had gone when it lets gas to the boiler?
The csi85 like all boilers have many safety features to prevent operation in the event that things are not correct.
I have grown to like the csi85 having spent more time with the boiler than my wife
I really dont understand why people like this want to bother doing illegal gas work for their friends.

A few of the jobs that I go to are where "friends" have messed up something and ended up costing the owner a lot more, including paying me to fix it.

If you want to help your friend why not do something legal and not very risky like digging his garden?

I had the same problem and found that if i disconnect the white wire on top of the condensate trap the boiler ran fine. There seemed to be dirt build up on the screw. I cleaned the screw and put the wire back in place and had no problems since.

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