Working on a cxi ultracom 24, my problem is the fault f9, I have 1.8 bar showing when I reset it, when the boiler starts up again Im sure I hear the divert vavle motor back and fore, but the fan does not run for the pre heat, after about a minute I get f9, had a faulty pump onces before and the boiler was still firering then locking out on f5, any idears or ways to check, many thanks