thank you all for your advice and support, the problem is sorted now, as i was expecting, the ignition P.C. B was faulty. I did more test on the boiler and concluded that was the fault. the reason for the ignition P.C.B to become faulty is the ignition electrode was lose and touch the top of the burner, where it should not, the gap should be 2-3 mm. as a result of this the electrical circuit was shortened, damaging the ignition P.C.B. and unfortunately there was not 3A fuse on the main electrical supply to the boiler. Whoever installed the boiler did not fallow the correct installation procedure and feed the boiler with 3A fuse box.
