Just changed the heat exchanger (an hour ago!) in my 80 as it was leaking (due to overheating) fortunately I have an old 80e which I used for the spares. These boilers have been a pain for me over the years, especially the 80e which I replaced (I own two flats) A few years back I spoke to a boffin at potterton and was told the electronics were poorly designed causing premature failure (I think in the relays) on the boards! The one I've just fixed is now switching off and on every few seconds (thermistors/sensors I think) and the Hot water flow is not as powerful as it should be which I need to look at! The cold supply has pleanty of pressure - might possibly be a restriction in the cold feed ball o fix valve, but probably something else! Not sure what ..diaphram?
Phil
November 2006