potterton prima f not igniting

[allenvb]

Dear all,
I was asked to look at a potterton prima, as it was not sparking, but the the fan was starting etc. After a few tests with the multimeter, it was decided that it was the control board. I replaced it and it worked fine, ignited and got upto temp, etc. I then got a call a few hours later saying that it was not igniting, but was going throught the rest of the sequence, fan starting etc, but no spark again.

Any ideas?

Thanks
V

 

[adlplumbing]

pcb

 

[Gas2Air]

Hmmm well you have to check APS n/o getting 240v, disconnect electode lead at the board, is there spark with a screwdriver near it, spark gap ok, lead and electrode ok?