Ariston 23 MFFI Combi Boiler - odd problem

[usher101]

Our Ariston 23 MFFI combi boiler has developed an strange problem, which the CORGI guy couldn't work out, so I thought I'd share it.

A couple of days ago, the boiler started to fire up and then immediately turn off, repeating this cycle until the whole unit was switched off. The CH is off, but the radiators are still heating up.

The CORGI guy couldn't see any obvious problem. the thermostat has been unplugged, but the problem remains.

thoughts?

thanks

S

 

[ChrisR]

HW flow switch stuck on?

 

[Rob]

Would have thought so too Chris but these use that reed switch and a small red LED is visable when operated.

 

[gas4you]

Chris, Rob, I dont know Aristons hardly at all apart from basic servicing and this may sound stupid, but if the hw switch is stuck I can understand the frequent firing up, but not the rads getting hot. Does the dv rest at ch position and is stuck there

 

[ChrisR]

Depends whether it's a EUROCOMBI 23mffi or a GENUS 23mffi - they're a bit different. I had to look it up - hence my question mark above!

The former has a normal diverter which rests in the CH position.
If it's a Genus I can't think of a single fault, which would make it do it.

 

[chrishutt]

I had a similar problem with a 23 MFFI a while back which I think had something to do with a loose connection around the main on-off switch to the bottom right of the fascia (raising and lowering the control panel affected it). Also worth checking the temperature sensors on these boilers.

 

[usher101]

ChrisR - it's a MicroCombi, according to all the documentation.

None of the indicator lights are flickering when it's on, so there's nothing obviously making a circuit.

Even with the CH dial turned right down to its minimum, it's producing some very hot radiators.

thanks for the collective puzzling,

S

 

[TonyWallingtonSM6]

//www.diynot.com/forums/viewtopic.php?p=1970399#1970399

I've had an Ariston EuroCombi A/27 combination boiler for over 10 years and for the past 4 months it has developed a fault - the Gas Central Heating would come on by iteself for approx 20 to 30 minutes & then turn itself off for a few hours before turning itself back on again etc... a constant cycle. This would happen throughout the day & night regardless if we turned the boiler just to hot water only.

Looking throughout the internet, one of the initial solutions was to change the Microswitch for 3-way/main flow group (its a £12.28 part 5733340) however this did not resolve the problem. Everywhere I looked there were different opinions on how to resolve so....

After speaking to a engineer who has worked on these boilers for over 20 years, he advised the above would not have resolved the problem as the central heating was coming on by itself regardless if anyone used hot water or not. The solution to the problem was either ;

A) The temperture probe for the central heating system needed replacing

e.g. if this was not working, the boiler would enter "Frost mode" , regardless if CH was turned on or not, so it would automatically come on every few hours to prevent the cold from freezing up pipes etc.... (original Part number 569236 but since replaced by part number 998458 £3.87 http://www.deansgas.co.uk/ariston-temperature-probe-998458-microcombi-23--27-10666-p.asp)

Or it would be

B) Faulty program clock


As the temperture probe was only £3.87, we tried A) & YES IT WORKED STRAIGHT AWAY ! & has continuned to work over the last 7 days

The reason I'm making this post is to help others who have the same problem with their bolier. This is a very reliable boiler so don' scrap it if you can fix this easily.

The www address for the part is shown under A) above & it really is very simple to replace (took 10 minutes in all)

 

[Agile]

This is at least your third posting about your boiler!

Just one new posting is all you need!