Ariston microgenus 11 31 MFFI

[dellcom21]

Help!!
I've got a problem with a microgenus 11 31 MFFI (not the condensing combi). The combi shuts down before room temp. is reached. the room 'stat is set to 21c but the boiler shuts down while the rads are cool. The boiler will sometimes fire up again and the cycle will start over but mostly the combi locks out showing a "A01" fault and has to be reset but, again, does not reach room temp. I checked max. and min. gas pressures and the gauge showed fluctuating gas pressure readings and you can also hear the gas valve solenoid operating with an intermittent "pinging" or ticking sound. I thought it was a flow problem but the pump is operating ok. Dom.hot water is ok and the boiler is about three years old. Any help or advice will be greatly appreciated.
thanks.

 

[Gasman28]

A01 fault is 'No flame after safety time - 7 seconds'
I would suspect a fault with the gas valve or possibly CH flow / return NTC's.

 

[dellcom21]

Thanks for your reply. I hope I don't seem too vague, but what are NTC's?
Cheers

 

[dellcom21]

further to my iniotial posting, some more information about the problem.
The boiler fires up on c/htg and reaches about 71 on the boiler temp. indicator. It the cuts out and the temp reading drops to about 58. It then fires back up to about 71 and the again cuts off. After about half hour the boiler locks out and when reset locks out again. I thought the dhw was ok but the boiler locks out after the boiler has been supplying hot water for a while. It wasn't evident at first because the dhw was not being drawn for a long period.
Could it be a circulation problem?
Any help will be greatly appreciated as I want to eliminate any system problem before I resort to replacing boiler parts.
Many thanks

 

[Rob]

Look through the sight glass to the burner when it's burning.

If you can see any sparking between the two electrodes once its lit then the PCB is faulty. Very common on this boiler.

The activities you describe about the heating temps etc seems normal operation.

 

[dellcom21]

Thanks Rob 884. It was as you said about sparking when the burner was lit. Changed the pcb and boiler now works. I now have a problem with the DHW.
I set the dip switch as per ariston with the fan over run selector on position "A" (on). The fan takes two minutes to shut down (normal?) but during that time if the hot tap is turned on, the burner will not ignite and an error code E33 appears. Once the fan is off, the burner ignites when the hot tap is turned on. hot water temp is 53-53. I've checked pressures and all ok.
Any ideas and info will be greatly appreciated.
Regards