the problem was that the customer put a 13amp fuse in the doube pole switch & the electrics went bang.
I was called out-no electrics to the boiler or programmer. Changed d. pole switch & put a 3amp fuse. Electrics now to boiler & programmer but fan will not light. Thought it might have blown the pcb & transformer replaced both still no joy. Blue light still flashing fast. Checked voltage to fan from pcb & got 230v. Do I now need to replace fan? Help would b appreciated.