ARISTON MICROGENUS 28 HE COMBI BOILER - E34 ERROR CODE?

I've had E33 and E34 error codes for years. This started a few years after the boiler was initially installed. At the beginning, when the codes first appeared and while still under warranty, I contacted Ariston who advised the codes relate to the air pressure switch but it was most likely to be a fan issue. They sent an engineer to replace the fan.

This fixed the issue.... for a while. All was well for a few years until it all started again.

It would only/always happen when the CH was running. Most of the time it was E34 and most annoyingly it would happen when opening up a hot tap. i.e. CH running. Open the hot tap to run a bath. Boiler cuts out and throws up E34 code. So so very very annoying!!!

When this started happening for the second time I was out of warranty so I did a little online research and got stuck in...

I'll point out that though not a gas engineer I am a plumber and I have some experience installing boilers under supervision. So I feel relatively competent carrying out non gas repairs myself.

I checked the fan to APS air tubes and the venturi for blockages. I replaced the APS, I removed the flue restrictor ring, I even removed the secondary air intake plug.

Initially some of these actions cured the issue in the short term. Replacing the APS made no difference at all but removing the restrictor and intake plug appeared to sort the issue... for a while.

When it started again a few weeks ago the seasonal cold showers and expletives started again. I searched the net yet again in the hope of new inspiration. I found another thread mentioning the resistance across the fan ought to be 40 Ohms but is often only 20 Ohms. I dismantled the boiler yet again and removed the fan to test it and give it a clean.

The resistance across the fan is 22 Ohms so I think i'd benefit from an upgrade however considering that the boiler works without fault until there i a demand for both hot water and CH and considering that the boiler did once work perfectly well with it's current components I thought I give the fan a thorough clean and refit it. why not.

I noticed that the delicate fan fins were caked with a thick layer of dust. I could not blow this dust off. It was really stuck on so I used electric element cleaner and a load of cotton buds. It took nearly two hours to carefully clean each fin.

Once shiny and clean, I sprayed lube onto the bearings then refitted the fan and screwed all the covers back in place.

I did this about 2 weeks ago. I've had no issues since!!

So that's it!! Cleaning those fan fins seems to have done the trick. I might still source and up rated fan but I'm going to leave it as it is for now to see how long it lasts.

Good luck

JTMac
November 2018

there is a good article explaining this problem that I found here:

http://www.urbanplumbers.co.uk/ariston-microgenus-24he-mffi-error-code-e33-e34/

Alex
September 2016

I've had intermittent e34 error on the 28 for years. Eventually going to permanent e34. Read this thread but decided to get British Gas engineer out, as didn't feel I knew enough to try and fix it myself. I told him what I'd read re. the fan and restrictor etc. His first thought was the fan. He cleaned out the fan and oiled it. Didn't fix it. He said it was fine to have the restictor on, according to what he was reading. He thought it might be the air pressure switch and I'd need new parts. But then he checked British Gas hints and tips, which he said is feedback from other engineers, and that also said to remove the restrictor; which then fixed it. He checked emissions which have now gone down since last service, due to the cleaner fan. He said he was looking at the manufacturer instructions and that's what said about the air pressure switch. They didn't say anything about the restrictor. If he hadn't checked he was going to order new parts, so I think a combo of me reading this thread, and him double checking has saved me a few bob. Took about 30 mins to do the lot. Cheers for the help guys :)

Kel
April 2016

Hi
I found the connector on the fan was blocked. Not a little bit, totally blocked. I removed the fan, took it apart, eventually got the pipe connector on the casing cleared. Put it all back together and it works fine now. This might be NZ s dirty lpg causing it

louis
September 2015

For Jack Frost: the chap was from a company called SDG based in Bedford. Try googling them but they are approved Ariston engineers. I found them by ringing ariston directly who can tell you who your local contractor is based on your postcode.

sb123
May 2013

I have just started getting the E34 and E33 errors on my Ariston HE combi boiler. At least it isnt too cold just yet to endure a half hot then freezing cold shower.

Thanks to this thread, Ive now removed the outer restrictor. Fingers crossed that this will be enough to stop it happening now as Im too scared to take the boiler apart further like most of you on this forum have done. :s

If anyone has time and energy - perhaps a video of some sort, teaching everyone how to take things apart would be useful? (legally of course - wouldnt want anyone non corgi registered fiddling with gas)

Frank
November 2012

To sb123
would you kindly tell us who this great engineer is and how to contact him so we can have our boilers fixed (cheaply, we hope) Also there is a manufacturing fault with the HE24 (cannot remember code, maybe 05 ) but it has to do with surges of electricity going down the left wire (of 3) as the boiler is switched on. The wires spark and a surge reaches the PCB burning it (costs £170 +inspection+works total £ 400) Ariston never replied to my complaints for reparations, have written twice with photos of offending wires, engineer's declaration, invoices for work/PCB...Nothing !! All one has to do is move the left wire away from the middle wire by a couple of centimetres by hand (3 seconds). Had Ariston isolated the wires during manufacturing it would not happen and we would save a lot of money. Not nice people this lot, will never buy ariston again.

jackfrost3
September 2012

I had the E34 and E33 error codes on my MicroGenus24 and today I had an engineer come out from the approved service list of Ariston and what can I say; the man is a legend.

He cured the problem and also explained why it was happening. He has fixed many of these in the same way and he got mine sorted in under 20 mins and then spent the rest of the time giving it a good tidy-up and once over.

I had had the restrictor ring from the flue removed perviously and the engineer removed a second restrictor ring which is situated in the secondary chamber which is joined to the fan. I think he referred to it as the recouperator. He explained the reason why my boiler had a secondary chamber as it was a late generation model and he explained that many boilers came fitted with both restrictor rings from the factory and that engineers when fitting were meant to remove them but they didn't bother reading the paperwork advising this.

The engineer has got one of these boilers himself so he knows lots about them and he warned me of things to keep an eye on. He also adjusted the high and low burn pressure settings are the previous engineer had ballsed them up. They apparently are set by 2 screws; one on top of the other and have to be set in order: high and then low so my boiler wasn't recieving the correct bar pressure of gas in order to fire correctly.

So if you've removed one restrictor then consider getting someone to remove the other one too. No need to change the APS straight off when this is easy and cheap to get done.

sb123
August 2012

I was working on this boiler and it came up with E34 and then E33. I replaced the fan and APS and checked for any blockages in the airways. The boiler still didn't work. I called Ariston and they told me to check the fan has 40 ohms of resistance across the terminals, which I found it didn't. It had 20 ohms. I went to the supplier and checked all of their fans which also had 20 ohms. I fitted a new fan again and still no luck. I then found that on the side of the APS you can change the sensitivity of it using a very small hex screwdriver. I made it more sensitive and the boiler started working. However, if the fan is at standstill and you open a hot tap there's no power to the fan and E34 comes up, but as soon as you close the hot tap the fan starts and if you open up a hot tap again the boiler works! So I'm thinking the problem is partly that their fans are underpowered and in this case possibly a PCB fault? Any ideas?

Orion
July 2012

Towlie's answer (sept 2011) is spot on, E34, it's the fan! wont go into what I did & time spent on this boiler (much the same as Towlie), but have apparently cured it by simply giving the fan motor a squirt with WD40! so far so good! "touch wood", seems to have cured it. if it works for you paste on other forums please.

jim c
February 2012

It's the second time in 5 years I've the same problem. 2 Years ago, I've get the E34 error. Thanks to similar forum as this, i check the condensate trap, and the problem was there. Yesterday, Another E34 error but this time, the condensate trap was not full of sediment...
After a little search, i've check the tube before the condensate trap (gray). It was full of sediment.. I've clean it and now it's Ok. I hope this can help someone :)

Sami (from Belgium)
February 2012

hi
Had same problems with my microgenus 24 error code e34 e33 tried various fixes air prssure switch etc did not solve the problem ,took the fan of all looked good not that dirty, gaskets ok but gave it a ( really ) good clean, put it back and problem solved so take note if the air preesure switch is not faulty its the fan.

roseland
October 2011

Also look here: http://www.ariston.co.uk/uploads/doc47f607e2c5a07.pdf

Mundek
September 2011

FINALLY MANAGER TO FIX THIS PROBLEM FAULT E34. Turn the boiler off, unscrew the flue where it meets the boiler, take out metal ring marked 43mm. this is an installation fault not a fault with the boiler. The 43mm ring is only supposed to be fitted where the flue is longer than 2 or 3 feet, short flues don't need it. Also I have just emptied condensate trap at the bottom of the unit on the left hand side. BOILER IS RUNNING FINE FOR A WEEK NOW. NO MORE ERROR E34.

Mundek
September 2011

hey everyone with a really crap ariston boiler i have all of the above problems!!!!! i have pretty much stripped and re built my micro genius. e34 had this occur after installed for 3 years. What it is not - (aps) air pressure switch or condensate trap. What the problem is - the fan which when new only creates just enough pressure for the boiler to work, as it ages it loses its edge which causes shut down e34.
To solve the problem.1 First see if the fan is running located at the top left of the boiler if you remove front cover you can hear it running or not. If running try remove and clean (vac and tooth brush)this might just be enough to create pressure, didint work for me but there is a chance. 2 remove restrictor ring in where the flue meets the boiler, this will require removing section of the flue to pull out the 45mm (what looks like a large metal washer this is normally removed on installation for flues over 3m, but works for shorter flues if fan loosing pressure. Mine worked fine after this for another year but once again the problem came back to haunt me e34 Ahhhhhh! Bought an uprated fan off better model. Now been working fine for 3 years no glitch. Problem with these boilers is the fan, no question. Conclusion? buy and install same fan, cost around £60 plus fitting. This will be fine for another 2 years. Uprate the fan ??? years (mine is great) buy new boiler and save yourself the heart ache!!
All i can say to everyone with thise34 problem is call plumber and ask him to replace fan unless you are confident! boilers are dangerous and cant put a price on saftey!! GOOD LUCK.

towlie
September 2011

Im having trouble with the code e33. can anyone advise me what is wrong please?

helen
March 2011

It is illegal to work on a gas appliance unless you are Gas Safe registered. Disconnecting the flue or condensate trap and not resealing correctly could be fatal. Please employ an expert. This is NOT a DIY job.

Gas Safe 514824
February 2011

Have had issues for 3months with intermittent hot water/radiators and sporadic E34 errors, finally had hardly any hot water and at best, slightly warm radiators.

Just fixed mine by removing a 5 inch round plastic plug/cover off the top of the boiler, above the fan. I doubt if this will cause any problem with fumes C02 or Carbon Monoxide as the fan is on when the boiler is heating, however I will be looking into getting a new fan as this is probably the real cause of the problem and will replace the plug.... Am I dicing with death?

davedefeet
February 2011

E34. It is an air pressure prob!
APS is a safety device,its doing its job, not that.
For it to work properly the fan must create a differentual pressure between the flue exaust and the air intake,its this that moves the switch (aps).
So your looking for restrictions to the flow, blocked flue, blocked venturi,dirty fan, maybe the fan is on its last legs.
Taking the restrictor out will solve the problem but dont throw it away because if you have a new fan fitted at a later date you may well have to put it back.
Hope this helps.

Nocharge.
December 2010

PLEASE do not remove the silver inner cover at any time when the boiler is switched on or in use. There is a danger of fumes, burns, or electrical shock.
The boilers are 'room sealed', meaning that the products of combustion (fumes) are safely directed through the flues to the outside air. Removing that cover provides that products of combustion may enter the room and be harmful to the occupants. This is classified as an 'IMMEDIATELY DANGEROUS' situation in Gas Safe Regulations and may harm you! It is serious.

The issue is not related to the condensate trap, as this is a A77 code. E33 & E34 relate to the draw of air from the fan/the draw of air affecting the air pressure switch operation/the fan venturis being blocked/the flue blocked etc.

These appliances can be dangerous if you don't understand them. Their design may, as many allege, have floors, but they have numerous safety devices to protect you from faulty operation. Be careful guys.

Rawson the Gas Safe Registered gasman
December 2010

Following the advice here and elsewhere I removed the flue restrictor and part emptied the condensate trap (which was NOT dirty or full of sediment). Boiler came on this evening and ran for an hour before the E34 error came on again.

Any other ideas?
Hot water only when heating is off!
Boiler is located in the garage.
Fan seems to to running.

David D
November 2010

We have just had this same fault show up tonight and have followed the advice to remove the restrictor in the flue and have cleaned the sediment bowl. The code has gone, I have hot water again and the cap doesn't blow out of the top when it fires up anymore. Thanks for the advice guys, much appreciated.

picalo
August 2010

As per Mickyp's answer, I emptied condensate trap on bottom left side of boiler (which was full of dirt water and sediment), and it solved the problem.
I think we should try this first before going any further....

Omar
August 2010

I had this error when I drained the system and replaced a radiator. After filling up the system and bleeding the air etc I found that after running the hot tap I would get intermittent hot water then the E34. As it is hot at the moment the central heating is off. By turning on the heating and leaving on for a while I found that the E34 had dissapeared. Now our hot water is consistent and no errors. Could this be that there was trapped air in the central heating pump part if the machine which also triggered the E34???

So If you haven't used your central hearing for a while and have air trapped somewhere in your boiler then try the above. Got rid of my E34!!

Anyway sorry to bore you lot!! Just my little contribution.

Paul T
June 2010

PLEASE NOTE the condencate trap should be full of water, its a water trap! thats the point! yes wash the sediment out of it but you MUST fill it half way up befor putting it back! if you put it back in empty, one you will get fumes blowing out of the flexable wast pipe, also if the boiler fires up on full power without water in that trap it can melt it! really if you dont know what your doing you shouldnt mess!

also the e34 fault is nothing to do with the trap! e34 is lack of airflow, on the 24kw you need to take the ristrictor out of the recouporator, where the fan enters it, 28 & 32 kw you need to take the ristrictor out the flue hood,

if problem persists on the 24kw the more powerfull fan off the 28/32 can be fitted!

thermoman
February 2010

had this E34 problem sorted today. the problem is a 43mm restrictor ring fitted inside where the flue meets the boiler it looks like a big metal washer 43mm in diameter. engineer who came to mine said that in the past he had spent over a day and a half on the first one he did because he replaced so many parts before he even looked at these rings, not all engineers know about this problem, i was charged only £30 and he was out of my house in 10 mins. you can fix this yourself. Turn the boiler off, unscrew the flue where it meets the boiler, take out metal ring marked 43mm. this is an installation fault not a fault with the boiler. The 43mm ring is only supposed to be fitted where the flue is longer than 2 or 3 feet, short flues don't need it

bigmomalove
February 2010

empty condensate trap on botom left side of boiler, this should solve problem.

mickyp
January 2010

Mine is a 32 HE - same problem. I've checked the air intake route and gas outlet route. No restrictions. Changed air flow switch. No difference. Examined fan and air flow switch pipework. Nothing untoward. Fan seems to run OK. Seals are OK.

If you give the boiler a little bit of help by allowing a very small leak of air past the cover the boiler works fine.

Conclusion - fan not powerful enough or has lost it's edge in it's first two years.

George
January 2010

J Man, where you having problems with your water temp too? I have just emptied the trap and was full so fingers crossed.

TJ
December 2009

I had this problem - the water wouldnt heat if the boiler was on ... with E34. I read the manual - there is a condensate trap at the bottom of the unit on the left hand side. I unscrewed mine (with a jug underneath) and it was fill of water and sediment - emptied it and screwed it back in and its working fine now....
Check this first - I just saved £70 a half hour for repair (clearly I am working in the wrong industry)

J Man
December 2009

Hi, this morning i've also had this error. i look at the flue restrictor but i founded none. I finally find out where the problem was. the condensate trap (where the condensate goes before it left the boiler) was full of limestone, so the condensate coulnd not be evacuate. I'd just to drain (there's a valve for) the trap. I hope my experiment can help.

Firestarter (from Belgium)
December 2009

Similiar problems with E34 error. If I took the covers off there was no problem. Fan has now been replaced and it's working fine.

Pieman
November 2009

I too have the same problem. It started about 1 yr ago. The boiler has just gone out of warranty, and I got the E34 error mostly, but sometimes E33. Called Ariston customer service and the lady (called Misba) was very rude. They did not want to know, but recommended a local approved plumber. Who came round, serviced the boiler, and left. I still get the same error codes. Not sure where to turn to really.

Mr Heaton
August 2009

I'm having an E34 error, I had it before two years ago, they came and replaced the PCB. It's nothing to do with the pressure sensor or flue, or restrictor, it's shoddy design. apparently they had to do it with most of the microgenus HFFI XX HE boilers from what I can tell. I'm also getting E33 errors too, it practically unusable, we have to boil water up with a kettle.
I'm going to phone them up tomorrow and complain. I'm demanding nothing short of a full replacement at their expense, this set of boilers are obviously not fit for purpose. Everyone should pursue method, get BBC Watchdog involved, they know these are faulty. What happens when people get to the end of the 5 year warranty, they simply buy a new one?
These things should be lasting 15 years minimum. Frankly I'm appalled and will never buy Ariston again, I curse the gas plumber who recommended and fitted the thing.

Christian
July 2009

Try this ebay seller - microswitch for £24.82 inc postage

http://stores.shop.ebay.co.uk/heatingsparesdistributors__W0QQ_armrsZ1

andy
July 2009

The air pressure switch is not closing could be:-

low pressure differential between flue inlet and outlet caused by

leaking fan seal or not seated properly
Dirty fan
blockage in the flue inlet or outlet (if the problem is borderline removing the restrictor helps)

OR defective pressure switch (diaphragm or switch)

andy
July 2009

Had same trouble myself changed aps made no difference had a serice engineer removed the flue restrictor , common fault on boiler.

taffy tuck
March 2009

The air pressure switch works fine, just fixed one of these boilers, the fan will NOT run if the air pressure switch isnt working but it clearly is, Fans not spinning fast enough, change the fan and it'll work. ;-p

Joe
January 2009

whatever you do dont leave the internal cover off the boiler is now in a dangerous condition! theres a danger of carbon monoxide entering the room, tried a new air press switch and it worked for ten minsthen back to square one,taking the internal cover off does get it to start so its either low fan speed , blocked venturi or ariston being their junk old selves anyone who worked on a eurocombie knows what i mean back tomoz for another go

howies helps
October 2008

I belive the tubes collapse to the switch causing a vacume. If you fire the boiler withe case off you will get error 33 which is the opposite effect to the possitive pressure

clive
September 2008

Hi

I know this probably was a fluke too, however, I turned it to "C" comfort mode and the problem has sorted itself... I hope

Andy R
September 2008

removed the flue restrictor this dosent solve the problem either

fonty
August 2008

had the same problem ive turned it to comfort mode and also left the sealed panel with the glass window in off and just put the white panel back. might be a fluke but mine seems to be ok now

jerry justice
August 2008

I have the same exact issue as all above. E34 pops up when the boiler should ignite.

Problem is worse when the boiler is already upto tempreture.

Have changed the air pressure switch but this made no different.... poor quality by Ariston by the sounds of it....

anyone found a fix yet?

Gavin Young
August 2008

JVR...has your problem been resolved? I am having the same problem with my boiler

AndyB
June 2008

Ask an engineer to clean out the venturi area,tubes etc.If this doesnt work,try removing the flue restrictor.

Your Welcome
March 2008

I have the same problem. I'm not convinced a new Air Pressure switch will resolve the problem. If I blow into the little inlet (remove black rubber cover on top of the boiler) to the air pressure switch the error clears but I can't stay there forever blowing into it. I'm waiting on a new part. The problem is worse when it's cold outside. I had another fault which I got repaired under warranty but it's now out of warranty. I'm not impressed by Ariston. I will report back if the new part resolves the problem.

jvr
March 2008

it means 'the air pressure switch does not close when the fan runs' (installation and servicing instructions). We had this error code on our boiler and it was happening because the outside flue had been knocked so air flow through the boiler was altered, its a safety thing and you need to get an authorised service centre to have look according to the manual. Hope this helps

Louise Arnold
January 2008

I too have the same boiler with the same problem! according to the manual this error code refers to the air pressure switch not closing when the fan runs. the cheapest I can obtain so far is about £54 including vat therefor I am trying to assertain if it is acctually the switch or something causing the switch to malfunction. hope this helps Tony

anthony steele
January 2008