Central Heating Not Working?

If your central heating isn't working, the cause can range from simple settings and low pressure to component faults like a failed pump or a stuck motorised valve. This UK guide walks through the most common causes, safe checks you can do yourself, and clear signs you should call a Gas Safe registered engineer.

Quick First Checks (Often Fixes It)

Check thermostat and programmer: Make sure the heating is on, the set temperature is higher than the room temp, and any schedules are correct.
Check boiler pressure: Many sealed systems should be around 1–1.5 bar when cold. Low pressure can stop heating.
Check radiator valves: Ensure TRVs and lockshields aren't fully closed on all radiators.
Reset the boiler once: If there's a lockout from a temporary issue, a single reset may restore operation.

Common Causes (and What They Look Like)

Symptoms can help narrow down the fault quickly.

Heating off but hot water works: Often points to a thermostat/programmer issue, a motorised valve, or the boiler not receiving a heating demand signal.
Some radiators cold: Could be trapped air, sludge, balancing issues, or a circulation problem.
Boiler fires then stops: Can indicate low pressure, flow issues, overheating, or a sensor fault.
Boiler shows an error code: Use the code as a clue and check your manual or manufacturer guidance for your model.

Step-by-Step Troubleshooting (Safe for Homeowners)

Work through these in order. Avoid opening the boiler casing or attempting gas-side repairs yourself.

Step 1 — Confirm the system is calling for heat

Turn the thermostat up and set the programmer to heating on. If you have a smart thermostat, check it has power and is connected.

Step 2 — Check boiler pressure and top up if needed

If the boiler pressure is below 1 bar when cold, the boiler may not run. Topping up via the filling loop often restores heating—if the pressure keeps dropping, investigate for leaks.

Step 3 — Bleed radiators if there are cold spots

If radiators are cold at the top and warm at the bottom, trapped air may be the issue. After bleeding, re-check boiler pressure and top up if necessary.

Step 4 — Check for obvious leaks

Look around radiators, valves and visible pipework. Even a small leak can cause pressure loss and heating failures over time.

When to Call an Engineer

Call a Gas Safe engineer if the boiler won't fire, keeps locking out, shows recurring error codes, is overheating, or you suspect a pump/valve fault. If you smell gas, follow official gas safety advice immediately.

Get the Right Boiler Size for Your Home

If you're considering a repair vs replacement decision, knowing a sensible kW range helps you compare quotes. Our boiler size calculator uses your property details and hot water needs to recommend a suitable output.

Use the Boiler Size Calculator

Frequently Asked Questions

Why do I have hot water but no heating?

This is commonly caused by thermostat/programmer settings or a fault with a motorised valve or controls that signal the boiler to run the heating circuit.

Can low boiler pressure stop central heating?

Yes. Many boilers have a low-pressure cut-out. If pressure is below the safe range, the boiler may lock out and stop heating until you top up.

Why are some radiators hot and others cold?

Trapped air, sludge, balancing problems, or partially closed valves can cause uneven heat. Bleeding and balancing can help, but persistent issues may require an engineer.

Should I reset my boiler if the heating stops?

Resetting once is reasonable if the boiler is in lockout due to a temporary issue. Avoid repeated resets if the fault returns quickly.

When is a heating problem an emergency?

If you smell gas, see signs of carbon monoxide concerns, notice burning smells, or there is significant leaking or overheating, treat it as an emergency and seek professional help immediately.