Why is my boiler not turning on?

Reasons why your boiler isn’t turning on or keeps turning itself off

Banner Logo

Reasons Why A Boiler Won’t Turn On

A boiler can refuse to start up or keep switching itself off for a variety of reasons such as: low boiler pressure, an air lock inside the pipes, a faulty thermostat, a closed valve restricting water or gas flow and a build up of sludge / debris inside the boiler system. In the event that a boiler detects a problem with the system, then it may switch itself off or not turn on at all as a preventative measure to stop further damage to the system and protect anyone in or around the property. As there are many reasons why this can occur you will need to investigate the problem further to rule out some possible causes.

boiler error code

Fault / error codes

The first thing that should be looked into is whether the boiler is displaying a fault / error code, this will be shown on the LCD boiler display screen if so. Obviously this isn’t always the case as older boilers will just show warning lights when shut down and really old boilers will just shut down without any sign or indicator given. 

When a boiler displays a fault code you can easily look this up in your user manual, or if you have misplaced your user manual there should be a digital version located on your boiler manufacturers website. 

If you have a fault code that identifies the problem but you don’t know the next steps to take, you can read our article on the most common boiler problems. Also feel free to call us on our customer service helpline quoting the fault code; this way we can advise the necessary measures that need to be taken and book an engineer appointment if needed.

Low boiler pressure

Low boiler pressure is often the culprit of a boiler lock-out which is easily solved. You will know if your boiler pressure is too low either by a fault code displayed, or by checking your pressure gauge which should be ideally on 1.5 bar but anywhere between 1 – 2 bar. For more information on low boiler pressure and how to re-pressurise your system read our article on the subject here.

Faulty thermostat

 Similarly, if you suspect a faulty thermostat you may be given a fault code, if not you can read our article on how to troubleshoot unresponsive thermostats to find out how to address the matter.  A faulty thermostat is another common malfunction that stops your boiler turning on, as if the thermostat isn’t working it won’t signal to the boiler to turn on as it usually would.

Faulty pilot light

Another complication that could be causing a boiler lock-out is a faulty pilot light, this will occur to prevent a build-up of gas in your boiler room resulting from a malfunctioning pilot light. You will most likely need an engineer visit if it is your pilot light, to know if this is the case make sure to read our article on pilot lights which will detail how to check if the pilot light has gone out.

Something else?

If low boiler pressure or a faulty thermostat isn’t the cause of your boiler lock-out then it is likely a more complicated issue that will need to be addressed by an engineer. Before booking an engineer appointment we would recommend consulting your user manual or calling your manufacturer to ensure all the valves are in the correct position. This can be the source of the problem but because every model and system is different, making it not something we could assist with unless we book an engineer appointment.

If you have gone through all these methods of troubleshooting and still not found the cause then you are going to need to have an engineer visit your property to carry out the correct repairs on your system. To get this matter addressed promptly call our 24/7 customer service helpline (0207 9989 005) and we will organise this visit to fit in with your schedule.