We are getting error code A01 when switching on our Ariston Micro-Genus boiler - can anyone tell us what this code means and if possible how it can be resolved?
Many thanks.

Louisa, August 2007

It is sometimes dirty jets. You need to see the flames properly. If they are not even you have blocked jets. Why? The jets near the sensor not working properly means the sensor doesn't work properly.

Louis, June 2021

Agree with Jim, my boiler would not light on DHW side only. It did this in very wet or damp weather, on first time ignitions, and not in dry or after running for a while. Water accumulating as Jim described. This then dries and the fault disappears. I don't doubt that the PCB can be damaged by the HT Spark feeding back either.

Griff, January 2018

Would people please stop posting that error A01 is anything else except for "No flame after safety time (7 seconds)" - that's from the boiler manual. I just did some work to clean out my recuperator and had a little accident and some water everywhere! I dried it all out but afterwards the boiler wouldn't start with error A01. The actual problem was a little droplet of water down near the spark generator - it seems it was causing the boiler not to open the gas supply hence no flame and shutdown for safety reasons.

Jim Reynolds, November 2017

If your boiler cuts out when the flame is on but it keeps sparking this is the very simple repair which will save you hundreds of pounds. I've made a short video which I have put on youtube for everyone. Hope it helps: https://www.youtube.com/watch?v=u-L3PzGQAa4

Clive Hancy, November 2016

i work at a community hall and this happens regularly we found that the majority of the time it was a case of the gas had been switched off or the lever had fell down no gas means no flame no flame means no boiler no boiler means program 5 err AO1 this is not always the case but it saves money ringing a specialist for something you might not think to check as the saying goes ("the microwaves not working" "well is it plugged in" "erm nope")

common sense guide, October 2016

How on earth can you have so many WILDLY different opinions!

mike, December 2014

hi im getting the a 01 code but it only shuts down when we put the hot water on

vinny, November 2013

Ao1 is caused by the flame sensor been too close to the burner tray which sometimes when the boiler tries to light the spark jumps off the tray to the flame sensor then travels down the line to the pcb which in turn shorts out 1 or 2 diodes on the board.
Donald Mcnaught explains the repair at the top.

Donald I would love to here from you as I wish to undertake your repair and would like to understand how you came to the conclusion on which to replace.

many thx

Gary Clark, May 2013

I replaced some capacitors on the main pcb of my Ariston Microgenus 28 MFFI boiler, it has worked for over 6 months without failure. I previously re-routed the flame monitor cable but the fault returned after a few weeks.
The capacitors I replaced were:
C900 10nF 400v polyester (Rapid 10-1860)
C901 47uF 35v Electrolytic (Rapid 11-3814)
C903 0.1uF 275v X2 type ac (Rapid 10-2675)
C904 10nF 400v polyester (Rapid 10-1860)
C905 0.22uF 400v polyester (Rapid 10-1865)
C906 100uF electrolytic 35v (Rapid 11-3816)
Cost of the capacitors was less than £3.00. (from www.rapidonline.com) One capacitor I bought had the wrong lead spacing but I managed to solder it in place.

Donald McNaught, June 2012

the A01 fault code is nearly always down to the pcb, 99% of the time in fact, its a common fault, but not common enough for ariston to be responsible for boilers out of the warantee. you can normaly check this yourself, while the tap is running check if the electrodes are still sparking even after the gas had lit, this means the pcb is not detecting the flame and trying to relight. eventualy it will lock out with a A01 code, if u reset it might work for a short time but eventualy u will get to the stage where it will no longer resart.

if your handy you can replace the pcb yourself, there is someone selling them on ebay for £85 thats a steel, its half the trade price never mind retail price!

pcb part number is 65103422 just search it on ebay!

thermo man, July 2009

Hello.This is a new and good one.My boiler(Genus 24) blinks ERR201 .
I have checked every possible source and the code doesn't exist.It's funny.

Dsl, January 2009

I have had the same problem, changed the PCB board which fixed the problem...for 3 days...having to restart it all the time now...

Sarah, July 2008

same problem with mine. plumber we rang asked if we were insured cos apparently its gonna cost a bomb to fix...and really cant afford it. boiler less than 2 years old..so surely this shouldnt happen.

em, July 2008

It could be a flue problem too - ours did the same recently and had an A01 and an A02 error after the plumber's visit. The roof flue had dropped slightly and was letting air in; the sensor thought it was CO and so kept shutting down the burners. With the flue now properly mounted, the problem has gone.

swanseagasman, October 2007

ao1- Shutdown due to igition failure. Press and release the "r" reset buton. If it fails to ignite check external gas cock is open. If problem persists consult an engineer.

j, September 2007

ao1- Shutdown due to igition failure. Press and release the "r" reset buton. If it fails to ignite check external gas cock is open. If problem persists consult an engineer.

j, September 2007

what do you mean it seems, it is either working or not.

ao1 is a pump problem
faulty or seized etc

hi-spec plumbing, August 2007

It seems that the circulation pump is working and there is gas flow. Is there anything else we should check?
Thanks!

Louisa, August 2007

ao1 is the circulation pump.

check to see is its working or faulty

hi-spec plumbing, August 2007