Hi. Boiler is three years old. Noticed recently that on full flow - from kitchen and bathroom tap - that water does not come as hot as it should. When flow is reduced, temp increases on both so filling the bath takes a little longer! I have set the temp at 60degC and on full flow forom either tap, but display show actual temp at around 50degC. I used a thermometer and actual temp from tap was 34degC. Flow rate measured at around11.5l/min and 10.5l/min at kitchen and bath tap respectively. (Measured with a bucket and stop watch as I don not have a weir gauge).There are occasions when the actual temp is showing 71degC but I cannot confirm the temp at the tap as only have a medical thermometer which just reads 'HI' beyond 42degC! I have gone through the fault finding in the manual and could deduce from this that it could be the NTC sensor or heat exchanger. I have inspected the heat exchanger visually and looks ok and clean. Pump and fan run and stop in correct sequence when they should do. I don't want to have to call anyone out if it's something I can do myself. I'd grateful for any help. Thanks