hello, My first post im a registered engineer, not used forms before so hoping I've posted this right? I have attended a no heat or water on my neighbours bias compact he combi, Fan would not opperate, they were no power at the fan and fuses good so I determined that is was a pcb fault. Replaced pcb- fan now operates but. Only fires for hw not for heat when called for, Also the actuator on diverter valve does not opperate. So I now believe that the air pressure switch maybe faulty as well as the diverter actuator. Could it be that these parts could have been damaged from a power surge when the pcb packed in?