Combi boiler problem

[Martin Pentreath]

It's that time of year I suppose, although this one is about the hot water, not the heating.

It's an Ariston Microgenus. It seems to have developed an intermittent fault whereby sometimes when you turn on a tap the hot water just doesn't get hot. While the hot tap is running there seems to be a lot of churning coming from the boiler, which I assume is the pump running, but neither the fan nor the burners come on. The "fume sensor" LED comes on until you turn the tap off, whereupon the light goes out again. This fume sensor LED seems to be a mystery from the research I've done. The manual doesn't say what exactly it senses. And I don't see how it can be sensing "fumes" because the burners aren't lit!

Any immediate ideas as to what would cause this to happen intermittently?

Cheers!

Martin

[A.Lee]

Has it got a pressurised container? If so, is the pressure high enough in the pressure vessel? I ask, as I had a similar problem with a Baxi a few months ago, I had drained all the water out to fit new rads, on refilling, the air pressure had all gone, so although the pressure gauge said it was fine, there was not enough air in it to allow the boiler to turn on for more than 10 seconds. It also made an awful lot of gurgling sounds as of there was a lot of air in the boiler. After a drain off of a few litres, then re-pressurise the vessel with a car pump, all was fine. Alan.