Boiler Keeps Cutting Out: 8 Common Causes

Quick Answer: Boilers cut out due to low pressure, frozen condensate, faulty thermostat, blocked flue, pump failure, overheating, ignition problems, or electrical issues. Some are DIY fixes, others need a Gas Safe engineer.

1. Low Boiler Pressure

DIY Fix ✓

Check the pressure gauge:

• Below 1 bar = too low
• Repressurise using filling loop
• If keeps dropping, you have a leak

2. Frozen Condensate Pipe

DIY Fix ✓

In cold weather:

• Pour warm water on external pipe
• Usually where it exits building
• Reset boiler afterward

3. Faulty Thermostat

Sometimes DIY ✓

Try:

• Replacing batteries in wireless thermostat
• Checking wiring connections
• Resetting thermostat to defaults

If still faulty, needs replacing by engineer.

4. Blocked/Damaged Flue

Needs Engineer ✗

Signs:

• Boiler cutting out after few minutes
• Unusual smell
• Debris around flue terminal

Important: Don't try to clear a blocked flue yourself.

5. Pump Failure

Needs Engineer ✗

Signs:

• Boiler fires but radiators stay cold
• Humming noise from pump
• Pump not running

Cost to replace: £250-£400

6. Overheating/Kettling

Needs Engineer ✗

Caused by:

• Limescale buildup
• Sludge in system
• Pump too slow

Usually requires powerflush (£350-£500)

7. Ignition Problems

Needs Engineer ✗

Signs:

• Clicking but no ignition
• Boiler lockout codes
• No flame visible

May need:

• Ignition electrode cleaning
• Gas valve repair
• New ignition leads

8. Electrical Issues

Needs Engineer ✗

Signs:

• Tripping circuit breaker
• Boiler dead (no display)
• Intermittent power

Could be:

• PCB failure (£300-£500)
• Wiring fault
• Fuse blown

When to Call an Engineer

Call immediately if:

• You smell gas
• Multiple reset attempts failed
• Boiler making unusual noises
• Error codes repeating
• No heat and you have vulnerable people

Glasgow boiler repair: +44 141 468 9930