when the central heating is on and try and turn to hot water on the fan/flu light flashes and no theres hot water..... after stopping to get hot water the fan/flu light keeps flashing... i reset the boiler and the central heating fires up... after a while boiler cuts out again with fan and flu light flashing.... but again after while the boiler will fire up as normal and work normally with all lights on. if i switch the central heating off for a while the hot water will work as normall.... . We dont have the heating on overnight and the hot water works fine in the morning, untill the central heating cuts in. The PSB was replaced last summer when again flu/fan fault light was flashing, and there was no hot water all. bloody boiler... thanks for any advice in advance.