Caution
A cold boiler should sit around 1 to 1.5 bar. Above 2 bar cold, or past 3 bar when it heats, means water has been added or cannot expand, and the relief valve may start dripping outside.
A boiler that fires, runs for a few seconds or minutes, then shuts down is protecting itself. Check the pressure and the radiators first, then reset it once.
Low risk
Water that starts hot and fades, or a boiler that shuts off while the tap runs, means it is not keeping up with the flow you are asking for.
Most boilers restart on their own once the power is back. If yours does not, check the switch beside it, the timer clock and the reset in that order.
The clicking is the boiler's igniter sparking. If there is no flame after a few tries it locks out. Check the gas is on and reset once, then call.
A gurgle is water moving past air or a partial blockage. Bleed the radiators and check the pressure, and in cold weather look at the condensate pipe.
A faint hum when the boiler runs is normal. A loud hum or vibration through the house usually means a tired pump or fan or a loose pipe or casing.
High risk
Switch the boiler off at the spur, put a container underneath and check the gauge. A leak inside the casing needs a Gas Safe engineer.
A boiler that fires with nothing calling for it usually has a reason: frost protection, a pre-heat setting, a smart thermostat or a tap dripping.
A dead screen is almost always a power problem. Check the fused spur switch and the fuse board before you assume the boiler has failed.
Switch the boiler off at its spur and reset the trip. If it holds, the boiler is the fault. If it still trips, the circuit is. Do not keep resetting.
Describe the job and get a fixed price from a local heating engineer.
