Boiler Not Firing Up? 6 Reasons Why Your Boiler Won’t Turn On (and How to Fix It)

A boiler not firing up suddenly can be a nuisance, a headache, or a nightmare — depending on how cold it is outside and how quickly your home loses heat.

Not only does a boiler flame failure stop heating your radiators, it leaves your taps and showers without hot water, too. 

In our 3-minute guide, we’ll dive into the 6 most common causes behind boiler ignition failures in gas boilers, and ways to fix them.

If you’re having trouble with your boiler not working for central heating or hot water, this guide will help uncover some potential issues, and what you should do next.

But first. Working on a gas appliance should only be done by a qualified engineer. If you’re looking for a repair or are considering a new boiler, you can get quotes here.

Boiler Is Not Firing Up – 6 Issues Behind a Broken Boiler

Below, we’ve listed the most common boiler problems that can lead to a boiler not firing up.

#1 – Faulty Gas Valve

The gas valve controls the flow of gas to your boiler. When more heat is needed, the valve opens to provide more fuel (and vice-versa when water gets up to temperature).

However, faults can occur with the gas valve such as:

• Blockages
• Seizures
• Damaged wired connections

A gas engineer can check for all the above. But, if your boiler isn’t igniting due to a gas valve issue, there’s a good chance the reason stems from incorrect adjustment.

When a boiler’s gas valve is incorrectly adjusted, it will lock out when supplied with too much gas (because it’s dangerous), or too little gas (because the boiler’s PCB recognises a gas supply issue).

#2 – Blocked Burner

Like combustion engines on cars, a boiler produces carbon when it burns gas. This gas can get clogged up in the burner, and will eventually mean that it runs inconsistently. Worse still is your boiler not firing up for central heating and hot water altogether–a distinct possibility if left unattended.

Unless the burner is damaged, cleaning out any carbon build-up will fix the issue. If the burner is in a bad state, it might be worth considering a replacement.

The problem with burner replacements is they’re not cheap. If your boiler is old and out of warranty, it might be worth looking into a replacement. Heatable is a company that offers exceptional deals on Worcester Bosch boilers, so we’d suggest getting on-screen prices here.

#3 – No Gas, Or Low Gas Pressure

A gas engineer can test for gas pressure at all the important places on the gas run:

• Into your gas meter
• Out of your meter
• To your boiler

Testing pressures here will determine if there’s a problem with the gas supply, and where that problem lies.

Like gas valve faults that give too much or too little gas, a boiler will lock out and display a fault code if the gas pressure isn’t correct.

On a side note, if your boiler only refuses to ignite during cold weather, there’s a good chance it’s the meter that’s the problem.

Gas meters have a regulator fitted to them. And, in low temperatures they can freeze.

The solution here is to lag the gas meter and regulator, to protect it from wintry conditions.

#4 – Electrode & Ignition Lead Problems

The electrode and ignition lead could be the issue if your boiler does not respond to thermostat adjustments, and then hear the boiler clicking but not igniting.

Gas related issues will create intermittent operation (i.e. the boiler ignites, and then goes straight off). However, without a functioning ignition lead and electrode, the boiler won’t ignite at all. You should call a Gas Safe engineer (or your boiler cover company helpline) and arrange for the boiler to be assessed. The inspecting engineer has the ability to spot electrode and ignition lead failures using a multi meter. If the fault lies with either of these parts, it’s much cheaper to replace them rather than to recondition them.

#5 – The Fan Isn’t Turning

When demanding hot water or heating, the first thing to operate will (or should be) the fan.

The fan in a boiler doesn’t cool down the boiler, it helps to create a draught. This draught pushes harmful gases from the boiler, into the flue. These gases are then taken out of your property.

If the PCB (the boiler’s circuit board) doesn’t recognise the fan is operational, it won’t ignite, and boiler lockout will instead occur.

The boiler ignition lockout procedure is put into place because it would be dangerous for the boiler to ignite.

If your boiler won’t turn on and you can’t hear the fan, this could be the issue. Fans are expensive so where possible, it’s worth reconditioning them (such as fitting a new motor), rather than replacing the whole unit.

#6 – The Boiler Pilot Light Keeps Going Out or Won’t Ignite

If the pilot light on your boiler has gone out, the cause is usually debris blocking the jet.

The jet for the pilot light is tiny. Even a small spec of dirt can block it, cause the pilot light to go out, and then the boiler won’t re-ignite.

These jets are cheap to replace, but they can usually be removed, cleaned and reinstalled to fix the problem.

What Else Can Cause A Boiler Ignition Failure? How to Turn On a Boiler?

There are hundreds of things that can cause a boiler ignition failure.

Your boiler has various fail-safes integrated into it (such as an air pressure switch). Whenever the boiler sees a signal that’s unusual, you will experience an ignition lockout — the boiler’s way of shutting down to avoid a hazardous situation. 

If your boiler is in lockout mode, it’ll most likely alert you with a corresponding fault indicator (these range between makes and models).

Resetting your boiler may temporarily turn off the alert, but your boiler will keep locking out as long as the underlying issue persists.

If you’ve had an ignition lockout, it’s best to call a licensed professional immediately and get your hardware examined. 

Also, your boiler may simply not start heating because your current temperature is already at the desired setting. To see if this is the case, simply turn the thermostat up several degrees, and see if this causes the boiler to ignite. 

We’ve created a boiler fault finding guide here, including guides relating to specific brands, boilers, and boiler parts.

If you want a generic overview of potential faults before investigating individual parts, we’ve created a guide to the most common heating and boiler problems here.

Boiler Still Not Firing Up?

If you’re having problems with your boiler not firing up for central heating or hot water, always consult an expert. You can get in touch with a Gas Safe registered engineer to fix your old boiler, or check out replacement quotes from Heatable here.

FAQs On Boilers Not Firing Up

As we wrap the post, we’d like to take the time to answer some common questions about boilers not firing up.

Why is my boiler not firing up?

If your boiler is unsuccessfully trying to fire up, the underlying issue has to do with either the gas supply or the working condition of the boiler. Common boiler problems leading to failed ignition include:

• Malfunctioning gas valve
• Blocked burner
• Insufficient gas pressure
• Problems with the electrode or ignition lead
• Faulty fan
• Pilot light not working

In either of the above scenarios, you’d need a Gas Safe registered boiler engineer to inspect your appliance and recommend a fix.

Now, note that if your boiler is off and refuses to fire up (i.e. without making any ignition attempts), it’s likely locked out. Lockouts happen because of problems that affect a boiler’s performance and safety. These may range from a blocked condensate pipe to issues with boiler pressure or other problems with the central heating system, and also require a Gas Safe engineer to be resolved.

How do I get the flame back on my boiler?

First, you’ll have to resolve the root cause behind your boiler not firing up, whether it’s a problem with the gas supply, burner, electrodes, pilot light, or anything else.

Once you get a Gas Safe registered engineer to fix the underlying problem, all you have to do is reset your boiler and it should fire up.

How long do boilers last?

You can expect modern, condensing boilers to last around 15 years.

However, not all boilers are made equal, so the best way to tell how long your boiler’s lifespan is, is to look at the warranty. Shorter warranties typically mean that the manufacturer assumes that their product will start malfunctioning after a short while, and vice versa. We’d recommend that you go with a boiler model that’s backed by at least a 5-year warranty, but the longer the better.

What’s Next?

We hope that our guide has answered your questions about why your boiler is not firing up. Do you feel that there’s something we’ve missed?

Or, would you like to share your own experience with a faulty boiler, or ask a question? If so, please leave a comment below and we’ll get back to you as soon as possible.