Ariston Eurocombi A23/MFFI multiple faults - advice please?

[magick777]

I have an ageing Ariston A23/MFFI that I can't really afford to keep alive, much less to replace. It has developed multiple faults over the course of 2-3 years that I've mostly learned to live with:

1) First the diverter valve diaphragm went. None of 6 plumbers I called would replace it, with two offering to replace the whole valve at a cost of a few hundred pounds and the rest preferring to replace the whole boiler, all for a £5 part. So I did nothing and lived with turning the heating on to get hot water.

2) Then the air pressure switch started to play up, so no heating or hot water without a vigorous thump on the top left of the boiler. More annoying, this one, but I've lived with it for a year or so figuring it reduces the gas bill.

I did try the local Ariston service centre, who also quoted me some fairly obscene prices, so again I did nothing. Now, tonight, it's put the wind up me; wouldn't fire up at all and no amount of thumping fixed it. Much cursing later, I had the front off the combustion chamber and blew into the pipes connected to the air pressure switch - which has fixed the problem at least temporarily and confirmed the air pressure switch as the suspect. So, now what, I ask myself? I'm a reasonable DIYer, but I'm no heating engineer and will have to RTFM to drain down and recommission the heating system. But, I'm not minded to pay somebody £300 to fit £25 in parts. So a few questions:

1) The air pressure switch looks like I can easily swap it out myself; does this sound like a reasonable thing to do and at what point should I decide that there is a need? Do they routinely live a while after such treatment, or is this a part on its way out?

2) I am a lot less confident about the diverter valve, but, I am tempted to learn. Am I likely to **** everything up if I calmly and methodically drain down the heating system, isolate the boiler, remove the valve and replace it with a new one? Since they sell the diaphragm separately, should I consider replacing it or are the locals right in saying replace the whole valve?

3) Does anyone have any comments on the lifespan of these boilers? I *really* cannot afford to replace the boiler right now and am very tempted to throw far smaller amounts of money (and larger amounts of time and hassle) at keeping this one alive. However, it must be ten years old at least, and I'm not sure how long I should pursue that policy before just finding some way to replace the bloody thing. Thoughts?

Thanks in advance for any advice / opinions...

 

[Gasguru]

The APS is contained within the combustion chamber which is generally considered a no go area for diyers, however,

It would appear the APS may have a problem but without measuring the contact resistance this can't be confirmed. It is also possible that there are other issues with air flow through the boiler and the APS is ok.

The diaphragm is normally an easy swap (just isolate the cold feed). However, you need to confirm the microswitch (on the end of the diverter) is not operating. If the diaphragm is swapped you may find the diverter is letting by ie. some heat is going to the radiators in DHW mode...not uncommon with a boiler this age, so a whole diverter may still require replacement.

I look after several A23's....not had to scrap any yet...all repairable so far. Typical other faults are clonking gas valves and the odd pcb. Leaks are also common on these boilers. Overall though they are a fairly robust boiler despite the slagging off most uninformed installers will give them.

 

[magick777]

Thank you; this is very helpful and it's good to hear someone say something other than "replace the boiler".

Regarding the APS, I don't have a multimeter so I'm thinking it may be wise to swap the ten-year-old, £21 part speculatively rather than pay someone to test it. My thinking is that 3 years ago it worked, 2 years ago it responded to a gentle thump, a year ago it responded to a violent blow and now it responds only to me blowing into the APS. On the balance of probabilities, replace the APS?

As to the diverter valve, the microswitch works fine when activated manually in DHW mode and, subject to the APS issue, it tries to fire up the boiler. The problem is that the pin doesn't extend far enough on DHW flow to activate the microswitch. I'm fairly sure that I need to replace the diaphragm and I'd like to have a go at doing so, but I'm not 100% confident of the best way to go about it.

Shutting down the cold inlet and the power is easy enough; I currently have the side and the front off the boiler, but am not sure how much of the DHW valve I need to unscrew/disconnect/remove in order to do the job.
I don't have access to the six screws around the offending diaphragm; the housing seems to be held onto the valve by two brass screws that I could remove, if and when I'm sure I know what the implications are and what to have done first.

How would you go about replacing the DHW valve diaphragm? Am I missing something obvious (I've read the service manual and can't find it)? Again, many thanks for your help.

 

[Boilerman2]

Keep the Ariston - just hope you have DEEP POCKETS!!

 

[Gasguru]

Shut off cold inlet.

Remove the 2 clips and pull out the 2 small pipes from the rear of the diaphragm section.

Loosen off the 2 screws and pull the diaphragm leftwards.

Remove all the screws around the periphery and replace the diaphragm...ensure the pin is clean from limescale.

Give me an old Eurocombi over all the carp on the market today.

 

[magick777]

Thank you, gasguru, that's perfect. Sounds doable enough, parts ordered.
I shall be a very happy man if £36 in parts and a couple of hours of my time fixes central heating and restores DHW on demand...[/i]

 

[mysteryman]

The fan could need cleaning. A non-satisfied APS doesn't necessarily mean the APS is faulty - it could be just doing its job. Make sure you put all the bits in the diaphragm assembly back in the same way round.

An interesting comparison with modern high quality boilers, though. I think the best current boilers are far better.

 

[Rob]

If it works when you wack it then chances are the APS isnt returning to the NC position.

The best boiler Ariston have ever made. I know that doesn't mean alot but well worth repairing.

 

[Agile]

I dont know whom the OP has been calling or if perhaps he thinks a repair charge over £30 is too high.

If anyone calls me about a diverter valve on this age of boiler then I quote to replace just the diaphragm but warn them that in many cases the manifold section is jammed and that it will still not operate correctly afterwards and need the whole valve replacing which will bring the total cost to about £200.

We dont encourage DIY gas work on this forum and that includes opening the combustion chamber.

Tony

 

[magick777]

I wouldn't regard a repair charge of even £100 plus parts as "too high", but I was quoted £270 and £350 just to replace the diverter valve, when the pin moved freely and it patently didn't need replacing, and before I ever had problems with the air pressure switch. This was some years back so I can't remember names, but the cheaper quote was from the recommended local Ariston service partner. This was from the minority who would admit that the job was even possible on an Ariston, with four out of six plumbers speculatively suggesting a powerflush and a new boiler at costs approaching £2,000, in response to being explicitly asked how much they would charge to replace a diverter valve diaphragm on an A23. Sadly, this casts the whole plumbing profession in an undeservedly bad light; it should have been a £50-£100 job to change the diaphragm, and if it had been, the same plumber would have got another £50-£100 job to change the APS.

Point taken about DIY gas work, I will not mess with things I don't understand and will not blame this forum if I do. With that said, the APS doesn't look like the most complex task I've ever seen, but, the caution is noted and appreciated.

 

[magick777]

I have a further question about airflow and the air pressure switch.

The new APS is in place and with the combustion chamber still open, everything works. The fan now fires up when CH is switched on, which it didn't before, and ignition happens after five to seven seconds. Until I put the front of the combustion chamber back on - whereupon the fan fires up, but (presumably) fails to satisfy the APS, because no ignition. Take the front off again, it all works. So, I seem to have gone from having a stuck APS to having a working but unsatisfied APS when everything is back together.

I'm somewhat lost as to what might be causing this; the fan is running and it all works fine with the cover open, but presumably I have some issue with airflow once the cover is closed. I've checked that the APS is of the same part number and specification as the previous one and that it's all connected up the same way. Any insights?

 

[Agile]

I wouldn't regard a repair charge of even £100 plus parts as "too high", but I was quoted £270 and £350 just to replace the diverter valve, when the pin moved freely and it patently didn't need replacing,

Point taken about DIY gas work, I will not mess with things I don't understand and will not blame this forum if I do. With that said, the APS doesn't look like the most complex task I've ever seen, but, the caution is noted and appreciated.

Because you dont appreciate how they work you come to that wrong conclusion!

Just because the pin moves that does not imply that the lower part is moving to follow it. They often dont on that age of boiler!

The APS is inside the combustion chamber. That is a sealed box which should not be opened by a non gas qualified person as if its leaking the potentially dangerous combustion products might enter the room.

Hopefully if you were in Japan you would not be going to open up a reactor cover to have a look inside at the safety devices?

Tony

 

[magick777]

Tony, with respect, and while I appreciate your concern...

1) I watched the valve fail over the course of a couple of years as it pushed the pin out first by 6mm, 5mm, 4mm, 3mm and slowly ceased to work as designed. Wouldn't surprise me if it has seized by now, and I'll cross that bridge if and when I come to it, but when I say it patently hadn't at the time, it patently hadn't.

2) I appreciate concern and common sense, but not scaremongering or dogma. I'm well aware that I'm replacing a safety device on the boiler, and how and why it needs to work. I'm also aware that my gas is burning nicely with a clean blue flame, that the fan is working, and that there's a CO detector about six feet from the boiler. Rest assured that I am more interested in my own safety and wellbeing than any of the "professionals" I contacted. Thank you again for your concern.

However, I'm more interested in why there does not seem to be sufficient airflow to satisfy the newly replaced APS, and am thinking the next sensible job is probably to clean the fan. I don't intend to bother with the diaphragm unless and until the boiler is back to working correctly in CH mode.

 

[Gasguru]

The APS is contained within the combustion chamber which is generally considered a no go area for diyers, however,

It would appear the APS may have a problem but without measuring the contact resistance this can't be confirmed. It is also possible that there are other issues with air flow through the boiler and the APS is ok.

Just in case you kill yourself I've CMA. An easy repair for competent boiler fixers.

 

[Agile]

Tony, with respect, and while I appreciate your concern...

1) I watched the valve fail over the course of a couple of years as it pushed the pin out first by 6mm, 5mm, 4mm, 3mm and slowly ceased to work as designed. Wouldn't surprise me if it has seized by now, and I'll cross that bridge if and when I come to it, but when I say it patently hadn't at the time, it patently hadn't.

Unfortunately you still dont understand what I am tyring to tell you!

That pin is only about 55 mm long and does not go all the way through the valve!

To operate properly the lower part has a similar pin and "follows" the pin.

If it does not do that then the valve is not working properly!

Just watching the short pin is NOT the entire story!

Tony