I have a Potterton Kingfisher gas boiler, probably about 15 years old.
It's given great service up until now, but the other day I noticed a
'flue-gas' smell in the house and sooty deposits on the outside wall
above the flue exit (there have never been any marks there before).
The boiler is regularly serviced (it was done just weeks ago) by a
reliable CORGI-registered gasfitter, who says there was no soot in the
exchanger when he last visited. He's just been back and apparently
there is now a lot of carbon in there. He's condemned the boiler and
says we need to replace it. But the burners look fine and nothing's
changed over the past few weeks.
Is it possible for a boiler suddenly to deteriorate like this? What
might be causing the carbonisation? Do I need a new one?
Grateful for any help you can offer!