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Gas Hob Won't Light
The burner clicks and you can hear gas, but nothing catches — or it lights and dies as soon as you let go.
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What's happening?
A modern gas hob has three things that must all work: gas at the burner, a spark to ignite it, and a flame supervision device that proves the flame is there. The flame supervision device is a small probe sitting in the flame; while it is hot it holds a valve open, and when it cools the valve shuts and the gas stops. That is why a burner that lights and then goes out the moment you release the knob is almost always a supervision fault, not an ignition one, while a burner that clicks and clicks without catching is usually ignition or a wet, dirty burner. The distinction matters because one is a clean-up and one is a part.
What usually causes it?
- Spilt liquid or cleaning water sitting in the spark electrode or the burner ports
- The burner cap refitted off-centre, so the spark is not reaching the gas
- A worn or cracked spark electrode, or a loose ignition lead behind the hob
- A failed flame supervision device or thermocouple, so the gas valve shuts as soon as you let go
- The knob released too early — most supervision devices need four to ten seconds held in to warm up
- A tripped RCD or unplugged supply, so the ignition circuit has no power even though gas is present
- An empty LPG bottle or a closed appliance isolation valve
Is it dangerous?
Low in itself, but there is one real risk: repeatedly clicking a burner that will not light releases unburnt gas into the kitchen. Stop after a couple of attempts, and if you can smell gas, stop entirely and ventilate. A burner that lights with a small bang after several tries has built up a pocket of gas, which is a reason to stop rather than to keep trying.
Can I fix it myself?
Cleaning and drying, yes. Take the pan support, cap and crown off a cold hob, wash and dry them fully, and clear the ports with a soft brush. Dry around the spark electrode carefully — a damp electrode is the single most common cause after cleaning day. Refit the cap square on the crown. Check the hob has power, that any isolation switch is on, and on LPG that the bottle is not empty. Hold the knob in for a good ten seconds after the burner lights. Anything inside the appliance is Gas Safe work.
When should you call a gas engineer?
Call a Gas Safe registered engineer if the burner still will not hold after drying and cleaning, if the spark has stopped altogether on one or all burners, or if you can smell gas at any point. Also call if the hob was recently installed or moved — a hose kinked behind the unit or a bayonet not fully seated shows up exactly like an ignition fault.
What will the gas engineer actually do?
- Confirm gas is present and at the right pressure at the appliance test point
- Test the flame supervision device and replace the thermocouple or interrupter where it has failed
- Replace worn spark electrodes and check the ignition module and leads
- Strip and clean the burner assembly, injectors and crowns
- Check the flexible connection, bayonet fitting and isolation valve behind the appliance
- Relight and prove every burner, then confirm the hob shuts down correctly on flame loss
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