Potteron Prima 50F fails to start normally

[tamste]

I have a Potterton Prima 50F NG that has been faultless for years.
Recently though it has developed a problem where it sometimes fail to start. This is getting worse to the point that it needs help most times.

What happens is that that when the control circuit calls for the boiler to start, the fan starts for a couple of seconds, then it switches off and repeats this fan start cycle over and over again without firing.

If I tap under the control knob buring the short fan running cycle (and get the timing right) the fan runs longer and the boiler starts up and runs as normal.

Any ideas what this might be please
Don't want to throw out an otherwise OK boiler if I don't need to but the wife and kids keep complaining !!

 

[namsag]

PCB has gone common fault on these

 

[picasso]

pcb needs changing

 

[picasso]

dam too slow

 

[tamste]

By PCB do you mean the Electronic boiler control unit?

If so are these easy to get hold of, and how much would I be looking to pay for one?

 

[tamste]

OK silly question. Have now established approx. prices for the PCB.

One remaining question though, can the pcb be replaced without opening up the sealed area, which I presume requires a CORGI registered engineer to complete?

I have noted a white wire that comes from the pcb and then goes into the sealed area above, hence the question.

BTW, thanks for the swift replies

 

[Eeejit]

white wire passes through rubber grommet and connects to spark
electrode. leave that in place, but disconnect from PCB when that is finally
removed.when you have disconnected all other leads, small-nosed pliers
may be helpful unclipping board from retaining lugs.