Since we moved into this house 6 months ago our boiler has failed 3
times. On each occasion the problem is a corroded earthing plate in
the igition system. This is the part that the spark jumps to to light
the pilot.

On each occasion the fitter refuses to believe that the part was
replaced on the last occasion, its in such a bad state. I rang the
tech advice at Potterton and they say we should check the polarity.
Fitter did that and says its OK.

The parts supplier the fitter used says the new replacement parts do
not have a long lifetime - but 3 months?

Anybody got any ideas?