I have a combination boiler that works well and has been serviced annually for the 3 years of it's life. Now the ECO button is on almost all the time. This means that when you want hot water the system runs, triggers the burner and you then need to wait for about half a minute for hot water. The button should work, to allow the boiler to heat a small reservoir of hot water to avoid the delay. When I press the button it works ok for a few minutes up to a few hours. It even worked for nearly a day, - but then it reverts of its own accord to "ECO" setting.
I am baffled. If I call in the company that fitted it and regularly service it, I am worried that their solution will be to change the whole control module and charge hundreds of quid for the pleasure.
Please does anyone have any ideas that might help to explain what is happening?