Arriston Microcombi Fault

[Foodface]

What does everyone think to this? Went to a gas safety inspection last week on a Arriston Microcombi 23 MFFI. All going well except when I go to do gas rates/flue gas analyses I noticed the boiler would fire up for a few minutes then just stop. Does the same on DHW too. Thought there was a fault with combustion so check inlet pressure etc, but when I had the boiler casing off I noticed the spark electrode would continue sparking then the boiler cuts out.


I’ve followed the alga rhythm in the booklet and I’ve decided to change the spark electrode and flame detection. I have a terrible feeling that something more serious may be at fault, so I continued along the alga rhythm to see what may cause it should the above not work (so I can prepare the customer for the worse) and two things came up.


Gas valve and PCB. If I fit the electrodes and the fault still occur, how can I determine for sure if it’s the PCB or the gas valve. Done boiler breakdown courses but still not 100% confident in instances like these.


Thanks in response


Foodface

 

[SimonJohns]

It's a retification fault

Have you got ionisation?
Is there a break in the ionisation wire?
Pcb poss dead after all that.

Could possibly be linked to a APS fault or dirty fan. I know these boilers can suffer when the have the restricter ring in the flue

 

[Ermintrude]

Mffi had a wiring harness fault? Ring tech to check but had to change harness due to induction voltages previously and boiler is fine.