More boiler advice please

[Martin Pentreath]

Hi,

I'm following up a thread on the ignition probems of my Ariston Microgenus combi (see

).

After following up the advice I was given by the group I've cleaned up the electrodes, cleaned the combustion area generally checked the HT leads and changed the spark generator. However, the bastard thing still has the intermittent ignition fault where occasionally it doesn't fire properly, and puts on its red light and won't do anything else until you press a button to reset it.

Following Raden's advice I've spent some time observing the boiler to try to work out exactly at what stage in the cycle things go wrong.

From what I can see through the little glass hole (which I've found to

be mainly more interesting than Saturday night telly) here's what happens. There's actually no problem with the spark. However sometimes only one "section" of the burners lights straight away - the flames don't spread all the way along. The other section usually lights a second or two later with a bit of a whoosh, I guess caused by the buildup of unburnt gas. I'm assuming (although because it's so intermittent I've not yet witnessed this) that the lockout is caused when the dodgy section of burners doesn't light at all (it's the section closest to where the detection electrode is) and the boiler gets worried.

So what's the remedy for this? A clean up of the burners? The combustion chamber did seem quite clean last time I was in there. At the end of the last thread Fred suggested the problem might be to do with the gas mixture, would my observations be consistent with that?

Cheers!

Martin

[Anthony R. Gold]

I had that exact problem with an Ariston Microgenus 23 MFFI. The problem was the gas valve, damaged by some additive to the UK gas supply that is not used in Italy where the units are made and that gums up the valve's movement to make it too slow to open and causes the ignition fail to time out and the red light to come on. The valve had to be replaced. If that's the problem it's a type fault a Corgi technician should recognise.

Sorry about the replacement PCB someone sold you.

Tony

[Newshound]

Had similar problems with a Wickes / Halstead. This has an internal nylon mesh filter on the inlet to the gas regulator valve which was full of what looked like graphite flakes. I discovered this on doing a full strip, but if you don't feel confident (or competent) to do that you may be able to disconnect the gas pipe at the valve and vacuum it.