my boiler is not heating properly ?

boiler flashes KL?
I doubt that very much
you must be misreading the display
you think it needs a "spark exchanger"?
no such part exists
I'm guessing you have an ideal ICOS HE18
which is flashing LF ( flame failure)
and you think it might need a SPARK ELECTRODE
that is one cause of flame failure but there are other possibilities as well

spark exchanger
April 2015