Hi, I have been having some problems with my Baxi 80 Eco which is about 10 years old and has served me well. At the moment when I use it for heating the system is very hot. The boiler itself is not hot and does not cut out but even though I have turned both (water and heating) dials to minimum the place heats up a lot. I can still use the heating, I just run it for about an hour and let the flat get nice and warm and then turn the heating part off, but obviously this is not good in the long term. When I first turn it on the boiler runs for a while and then starts to cycle. So it might come on for 10 seconds then turn off for 30 seconds then come on again for another 10 seconds and continue like that. The heating control seems to work, in that if I turn it up the boiler stays on for longer and I think the heating gets even hotter. What is odd is that this also happens if I turn the water heat up even if I am not using any water. The water control dial does seem to work very well for water. If I turn it to minimum I only get tepid water but turn it halfway and the water is nice and hot so my problem is only on the central heating side. As mentioned though I do need to keep the water dial turned to minimum when using heating so that is a bit of a pain as every time I want hot water I have to go and turn it up. I do not have temperature controls on the radiators (well only on a couple and they don't seem to work very well) but this has been the set-up for the ten years since the boiler was installed and I always controlled the heat satisfactorily by using the dial on the boiler. The history is that I have had very little trouble with this boiler apart from loss of pressure. This gradually got worse and during the winter I was topping up the pressure on a regular basis whilst noticing overflows anytime the boiler was on high. I had an engineer look at this about two years ago and he changed the pressure release valve. This seemed to help a bit but not much. He came with some pressurised gas but was unable to use this. He said if the problem continued he would come and fix an external pressure thingy on the wall. I phoned and asked him to do this but even though I called several times he never turned up. So I lived with it for a while. The heating was good all winter, I just kept it on most of the time on a low setting and that was OK but I did not use the timer as I wanted to keep an eye on the pressure. Then at the end of the winter this problem of the heating getting high and the boiler cycling started and I had a lot of water on my step where it was overflowing. I got another engineer in and he changed the pressure valve again and did something with a footpump to increase the pressure which has worked very well as the pressure is now stable. I told him about the problem with the heating always being high. He thought this was something to do with the microswitch (diverter valve?) on the left hand side and said he would look for one and call me back. Unfortunately he has not done so. I think he probably decided it wasn't the diverter valve anyway. I have had a good look at it and it seems to work well. When I turn a hot tap on the switch is activated and I have no problem with hot water so I think that is OK. Does anybody have any ideas as to what could be causing my central heating to get so hot? If I can work out what the problem is I will order the parts and then get a proper gas engineer to come and fit them. I am a trained electronics engineer so could try swapping out the PCB but anything else I would not be confident about doing myself. I just don't want to keep getting engineers out if they seem uncertain about what the problem might be so wanted to see if anybody here has experienced similar problems.