Worcester Bosch 24i - Flame Detection Failiure?

[elche286]

Hi new here so treat me kindly!

WB 24i junior. Had it about 4 years - no probs. Nothing changed recently. Seem to be having the same fault as other people have mentioned. Sometimes in demand mode for both CH + HW (either together or seperate) it will go thru the ignitition sequence as per page 31 but burner stops after about 7 seconds.

The flame sensor is in the flame, the lead is secure at both ends.

I got a friend coming round tonight so he can check the continuity of the flame detection harness and i will also ask him to check polarity.

But my question is this - I just get up this morning (not partic cold) and the 7 sec burn fault that was happening last night is clearly intermittent as boiler just burned for approx 7 mins without any flame cut out.

I have access to another 24i and could switch the pCB to check if this is it - BUT my question is.... if the fault is intermittent is it more likely to be flame sensor or pcb or something else entirely? Surely pcb's either work or not i.e. not intermitently

Thanks in advance

 

[Agile]

Apart from measuring continuity from sensor tip to PCB there is little elsy you are likely to be able to do apart from swapping the PCB.

There are a lot of faults with the PCB but that is not one of the most common.

If you burn a lot of candles then you may have a carbon buildup on the PCB at the right hand end around the flame detection circuit.

I found that in a Hindoo Temple boiler !

Tony