A boiler that will not fire up is either not being asked to run, not getting what it needs to burn safely, or shutting itself down because a safety device has tripped. Working through the simple causes first often saves a call-out.
Checks you can safely make
- Confirm the thermostat is calling for heat and the batteries are not flat
- Check the programmer or timer is on and set to the right day and time
- Check the boiler pressure gauge reads roughly 1.0 to 1.5 bar when cold
- Make sure the gas supply is on and other gas appliances still work
- Check the fused spur or plug supplying the boiler has not tripped
- Look for a fault code or lockout light on the boiler display
Common faults behind a no-ignition boiler
If the basics are fine, the fault is usually inside the appliance. We regularly find failed ignition leads and electrodes, blocked or contaminated flame sensors, a faulty gas valve, a failing fan or air pressure switch, a blocked condensate pipe in cold weather, or a PCB that has stopped driving the ignition sequence.
The boiler lights then cuts out
A boiler that fires for a few seconds and then locks out is normally failing to prove the flame. That points to the flame sensing electrode, poor combustion or a flue and condensate issue - all of which need testing with the correct equipment.
Reset the boiler once. If it locks out again, stop and call an engineer. Repeated resets can hide a genuine safety fault. If you can smell gas, call the National Gas Emergency Service on 0800 111 999.
When to call us
If the controls and pressure are correct and the boiler still will not run, we will diagnose it properly and quote before any work goes ahead. Most repairs are completed on the first visit because our vans carry the common spares.
Written by the engineering team at Newcastle Boiler Maintenance Ltd, Gas Safe registered heating engineers in Newcastle upon Tyne.