🔍 Why Does My Boiler Keep Switching Off?
| Cause | Symptoms | Fix |
|---|---|---|
| Low water pressure | Pressure below 1 bar, boiler cuts out | Repressurise system |
| Faulty thermostat | Boiler fires then cuts out quickly | Replace thermostat |
| Frozen condensate pipe | Cuts out in cold weather | Thaw pipe, reset |
| Blocked flue | Boiler locks out, error code | Engineer required |
| Faulty pump | Boiler overheats and cuts out | Engineer required |
| Airlocks in system | Boiler fires then cuts out | Bleed radiators |
| PCB fault | Random cutouts, error codes | Engineer required |
✅ Check These Yourself First
Step 1 — Check the pressure
Look at the pressure gauge on the front of the boiler. It should read between 1.0 and 1.5 bar. If it's below 1, repressurise using the filling loop.
Step 2 — Check the thermostat
Make sure your room thermostat is set above the current room temperature. If it's a wireless thermostat, replace the batteries.
Step 3 — Check for error codes
Most modern boilers display a fault code when they lock out. Note the code and search our error code guides for Worcester Bosch or Vaillant.
Step 4 — Try a reset
Press the reset button once. If the boiler fires up and then cuts out again within 10 minutes, don't keep resetting — call an engineer.
Never reset a boiler more than twice. Repeated resets can damage the gas valve and turn a minor fault into an expensive repair.
💷 How Much Does It Cost to Fix?
| Fault | Typical Repair Cost |
|---|---|
| Pressure issue / condensate | £80 – £110 |
| Thermostat replacement | £100 – £200 |
| Pump replacement | £200 – £350 |
| PCB replacement | £250 – £450 |
| Gas valve replacement | £250 – £400 |
FE Maintenance provides a fixed price quote before starting any work — no surprise bills. Call 020 8445 1303 for a same-day diagnosis.
Frequently Asked Questions
This is usually a flame detection fault — the boiler lights but the flame sensor doesn't detect the flame and shuts the boiler down as a safety measure. Common causes include a dirty or faulty flame sensor, ignition electrode fault, or gas valve issue. Call FE Maintenance on 020 8445 1303.
In cold weather, the most likely cause is a frozen condensate pipe. This is the white plastic pipe that exits through an outside wall. Pour warm water on it and press the reset button. If it keeps happening, the pipe needs insulating — FE Maintenance can do this during a service.
No — you should only reset once or twice. If the boiler keeps cutting out, it's doing so as a safety measure because it has detected a fault. Repeatedly resetting can mask a dangerous problem and potentially damage components. Call a Gas Safe engineer.
Yes — if your gas pressure is too low, the boiler won't get enough gas to maintain the flame and will cut out. Check if other gas appliances work normally. If your gas hob also has a weak flame, call National Gas on 0800 111 999. If it's just the boiler, call FE Maintenance.
We offer same-day appointments across London. In most cases we can diagnose and fix the fault in a single visit. Call 020 8445 1303 before noon for a same-day appointment.
📚 Related Guides
Need a Gas Safe Engineer in London?
FE Maintenance — trusted by hundreds of London homeowners and landlords. Same-day appointments available.
Gas Safe Reg. No. 587248 · info@femaintenance.com