Vaillant TURBOmax VUW 242E/282E Hot Water Problem?

Faulty hot water microswitch on the diverter valve or problem with the diverter valve itself. The microswitch is cheap and easy to change. The valve could have a faulty diaphragm or broken armature [made of plastic and prone to breaking on this model]. It is best to replace the valve complete as their a pig to work on and if your paying someone its quicker to do so less labour costs.