Ferroli Domicondens spark electrode fault

[kasser]

Does anyone have any experience with resolving an A02 fault?
"Flame present signal with burner off."
Possible cause: electrode or card fault.

It usually starts with an error code regarding no flame after ignition phase and is replaced by A02. I had a gas valve fault being displayed but got rid of it by resetting the boiler.

The boiler is 6 years old. It's not possible to use a spark tester as there is nowhere to disconnect the spark electrode. The resistance from the lead to the tip of the spark generator is 0.99 k ohms, seems high for what is just a lead? The voltage at PCB connection was 0 but is it supposed to be 240 V all the time? I inspected the gap and cleaned the tip of the electrode.

By resetting it multiple times, I managed to get the boiler to fire up and work nicely for a short time before the error came up again. Wouldn't that indicate that the spark electrode is not defective?

In fact, a few months ago I had the same issue and it disappeared until now after I reset it a few times. I had called the manufacturer then but they were not helpful other than reading the manual.

 

[AMGasServices]

If you’re getting it to fire by resetting it a few times it seems that your electrodes are fine.

Remove the gas valve and check if its full of shale (little black particles). Pretty common these day. What’s the working pressure at the meter and boiler ?

If the above is ok then it’s possibly a PCB fault.

 

[kasser]

I wouldn't be able to get the boiler to work long enough to measure the working pressure.
I'll try checking the gas valve. I was focusing on the spark electrode because of the error description.

 

[AMGasServices]

If It sparks but doesn’t stay on its doesn’t appear to be rectifying. Then your looking at you’re flame rectification electrode.

Also is your condensate trap clear ?

 

[kasser]

I don't think there's a rectifier there. I can see just one electrode. No return path for the signal.

 

[AMGasServices]

Ok cool it uses the same electrode for the spark and rectification.

Do you get a strong spark or is it weak?

Do you have a good earth to the boiler?

I’m thinking it’s the PCB.

 

[kasser]

When it's the same electrode for rectification, how does the rectified signal travel back? Surely not through the same conductor?

I thought it would be the PCB because I had the same situation in Aug and it worked fine after resetting it a few times, so nothing broken with the spark. But I thought when PCBs broke down, they just failed completely?

Just noticed your mention about the condensate trap - easy one to check and clean but how does this affect the electrode?

 

[AMGasServices]

If it full of muck or clocked most boiler may spark and lock out. Some have a switch/sensors other work in air pressure to the gas valve etc...

 

[kasser]

Thanks, will buy spare electrode and pcb first thing tomorrow and follow the checks you recommended before replacing anything.