I have a Vokera Excell 80 SP that has developeda fault. The central heating
stays on regardless of the temprature setting on the thermostat and stays on
even when the bolier is switched to summer \ water only mode.

I tried following the flow diagrams in the manual and this led to replacing
the easiet to replace but unfortunately the most expensive part, the PCB.
However, this has made no difference. Heating still fires up in both modes,
only way to turn it off temporarily (without setting the mode selector to
off) is by turning the central heating temperature setting dial on the
bolier to the minumum setting. Only problem with that is that the hot water
dosent work at the setting as it only seems to come when the heating is
fired up.

Any ideas?