Boiler Not Working? The Six Most Common Faults
What the fault code is really telling you, what's safe to try, and when to stop.
Low pressure
The gauge below 1 bar is the most common no-heat cause. Repressurise via the filling loop to 1.2–1.5 bar. Needing to do it more than every few months means water is going somewhere, that's a leak, not a habit.
Frozen condensate pipe
The white overflow pipe outside freezes in a cold snap and locks the boiler out. Pour warm (not boiling) water along it, reset, and it usually comes straight back. Lag it so it doesn't recur.
Everything else
Failed diverter valves, seized pumps, faulty ignition and scaled heat exchangers all present as codes on the display. The code plus the make is genuinely useful information, have it ready when you call. Anything behind the case is Gas Safe territory: not a DIY frontier.
When to stop trying
Smell gas, see soot marks, or hear the CO alarm, stop, open windows, call 0800 111 999 before anyone else. Nothing on a screen is worth testing past that point.