Hi,

My Potterton Profile 50e has been starting only intermittently recently.
I've been trying to figure out what the problem is using the handy
fault finding chart at the back of the boiler manual, but I'm not too
sure exactly what the problem is.

When I call for heat, I hear the fan switch on (not cycling on/off, it's
on continuously). Up until a couple of weeks ago I'd get one or more
sparks from the electrode - sometimes the pilot would light first try,
sometimes it wouldn't light at all. If it doesn't light after 3 or 4
attempts, the fan will keep going but ignition will stop. Usually, by
switching off then switching on, it'll light on the second or third
attempt.

However, it's been deteriorating recently - I'm now rarely getting any
ignition sparks. Also, on one of the ignition attempts this morning, I
noticed that the pilot light started up but then died out a couple of
seconds later.

One slightly disturbing thing I noticed when listening carefully this
afternoon was that after the fan starts up and before the ignition
attempts, there is a electric buzzing/crackling sound, as if electricity
is arcing somewhere.

From the fault finding chart, that puts my problem at either a leaking
case door, a problem with the electrode lead, a problem with the
electronic control, a problem with a blocked pilot jet, or a problem with
the solenoid.

Does anyone have any suggestions where/how I should start isolating the
fault, or for what the problem could be?