intermittant hot water

Hi mike

I have a problem with hot water in that it starts hot then goes cool but not cold, Have cleaned in line filter but it hasn't helped. Read on your forum that it could be the hot water sensor, the store temperature sensor or the plate heat exchanger, but when running, the exchanger and pipe work to the pump is red hot then goes cool but the top of the exchanger is still very hot. If it's the heat exchanger how easy is it to change? can you help

thanks very much good web site

paul eacott

boilermate 111, year of make 2000, type BM180

BM III has a coil not a heat exchanger.
Or have you a BM2000?
Mike