Water goes hot then cold when running tap?

My water (halstead ace he 30) runs hot then cold not very hot at that. Central hearing works fine. If we have a shower we get about a minute of warm water then it runs cold for a minute then warm again. Any ideas?
Robin, December 2012


done
you need to put a system cleaner in.its the heat exchanger that is the problem.(limescale}

dai, December 2012
blocked dhw heat exchanger. has become scaled either replace or get it cleaned.

kash, December 2012
link Click here to see other fixes for Halstead.