how can i re-ignite my pilot light on potterton netaheat boiler?

THE PILOT ON THE NETAHEATS ARE NOT PERMANALTY ON THE FAN STARTS, FIRST CREATES PRESSURE IN THE CASE WHICH WORKS A PRESSURE SWITCH, THIS IN TURNS STARTS THE IGNITION AND THE PILOT SHOULD SELF LITE IF FAN RUNS AND NOTHING ELSE COULD BE A FAULTY PRESSURE SWITCH OR SOME TIMES IF YOU HEAR A SPARK THE EARTH ROD HAS CORRODED THROUGH

RAY
April 2007