Home / Guides / Boiler Problems
If your boiler stops working, there are a few safe checks you can make, such as pressure, thermostat settings and the power supply. If you smell gas or suspect carbon monoxide, stop and get help straight away.
✓ Safe checks you can make
✓ When to call an engineer
✓ What to do about gas smells
Tell us what you need and we will come back to you.
If you smell gas, or your carbon monoxide alarm sounds, do not use the boiler. Open doors and windows, leave the property and call the National Gas Emergency Service on 0800 111 999. Never ignore a carbon monoxide alarm, and do not switch lights or appliances on or off while you are waiting.
Never take the cover off a gas boiler or attempt gas repairs yourself. The checks below are all things you can do from the outside, using the controls and the manual.
✓ Gas Safe registered engineers
✓ 20+ years of industry experience
✓ Local, Bury St Edmunds based
✓ Honest, no-pressure advice
✓ Neat, tidy installation
Make sure the boiler is switched on, the thermostat is set above room temperature and the timer is correct.
Most boilers need a pressure of about 1 to 2 bar when cold. Your manual explains how to top it up safely.
Look at the display and your manual to see what the code means.
In freezing weather the outside pipe can freeze, which shuts the boiler down. Warm water poured over it often clears it.
If the manual says it is safe, press the reset button once.
Often a thermostat, timer, pressure or power issue, or a failed part such as a pump or valve.
Trapped air is a common cause, and bleeding the radiator often helps.
Sludge or debris can build up in the system and may need a professional clean.
Banging or whistling can point to air, limescale or a failing component.
A slow leak or a faulty expansion vessel or valve is the usual cause.
Low pressure, a blocked condensate pipe or a fault in the controls can all cause lockouts.
If a radiator is warm at the bottom and cold at the top, air has probably collected inside. Turn the heating off and let the system cool, then use a radiator key to open the bleed valve slowly until you hear the hiss of air stop and a little water appears. Close the valve, then check the boiler pressure, because bleeding can lower it.
If you have to bleed the same radiator repeatedly, or the water that comes out is black, there may be a deeper problem such as sludge or corrosion in the system. That is worth having looked at.
If the problem returns, the pressure keeps dropping, you see leaks, or you hear unusual noises, it is time to call a qualified engineer. Repeated resets can hide a fault that needs proper attention, and a boiler that keeps locking out is telling you something.
When you call, have the make, model and any error code to hand, and note what you have already checked. It helps us arrive prepared and often shortens the visit. If the boiler is old and keeps failing, our guide on whether to repair or replace it may help.
Can’t see your question? Send us an enquiry using the form at the top of the page and we will come back to you.
Trapped air is a common cause and bleeding the radiator often helps.
There may be a leak or a faulty part, and it should be checked by an engineer.
One reset is usually fine if your manual says so. If it keeps locking out, there is an underlying fault and you should call an engineer.
If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency Service. Otherwise, turn the boiler off and get it checked.
Call 07549 400152 or send an enquiry online.
