boiler keeps trying to fire up even though it is runnin
the photoresistance keeps choking up with soot a wipe cures the problem .

roy, March 2009

it keeps sparking (I presume that's what you mean) cos that photocell can't see light, presumably cos it's sooted up.

When was the boiler last serviced? It shouldn't run sooty, if it is then there's a chance that it's either wrongly set up, your oil is contaminated or it's just never been serviced and needs a good old clean.

Bunslinger, March 2009