A 3 year old Ecotec plus 824 Vaillant has developed the following- when running hot water to the bath or sink the water will pretty quickly run hot but after a minute runs cold for a while then runs hot again and repeats. Can anyone diagnose the fault and indicate what repairs/settings needed. thanks
Had the work done and it turned out to be a blocked heat interchanger unit- not the diverter valve. Job cost £262 but the engineer said it would be possible to clear the unit of gunge and it would be reusable!