When you open the hot water tap there is no ignition. I checked the diverter valve and that is ok the pin comes up and operates the microswitches. I also tried another ignitor pcb but still same problem. Then I noticed once I tap the boiler on the side it works theres hot water and central heating works. From further inspection I came down to the multifunctional control sit (Gas Valve). When I open the hot water tap or put the central heating on there is no ignition but once I tap the gas valve gently then it starts to work. Is the gas valve faulty and need replacing? Has anyone else had this problem?