Common boiler problems

Boilers have a series of control mechanisms designed to distribute heat and hot water at peak times. Faults with these controls can run up your fuel bills and make your home uncomfortably hot or cold.

Simple checks to your thermostat, programmer and time switches, the electronic programmer and radiator valve may help to get your boiler up and running.


Don't ever attempt to do any complex servicing or repair work on your heating system yourself – always seek the skills of a Gas Safe Register approved heating engineer. And keep in mind that all boilers and heating systems should be serviced and checked regularly by a professional. This will prevent any future problems and expensive emergency call outs.


Check the age of your thermostat. Over time they can lose their accuracy, misreading temperature settings and turning the heat on/off at incorrect times. Be advised that while a gas boiler engineer can clean and recalibrate your old thermostat, it might be wise to purchase a new one with extra energy-saving controls at your local DIY store.

Setback and programmable thermostats warm your house when you need it and turn the heat down when you don't – they can cut heating bills by 10 to 20 percent.

Programmers and time switches

These are mechanical time-clock driven programmers. Check that the clock dial isn't stuck. If so, the program on/off timing will be wrong. The hot water and heating are controllable via the timed/off/constant switches found on your boiler.

Electronic programmers

Check that the LCD display, circuit board electronics or relay hasn't failed. If you already have a standard universal backplate behind a failed electronic one, a replacement usually just plugs straight in its place (the same way a plug fits into a socket). These can be found at most DIY stores. Simply remove the retaining screws holding the unit onto the backplate.

Radiator valve

If you have a thermostatic valve, turn up the thermostat. If you have a conventional lock shield valve, remove the plastic cover and adjust the setting.

If no change occurs after you've adjusted the settings, you have a fault with your radiator valve and will need to call a Gas Safe Register professional to drain the system and replace it.

Condensate pipe

A condensate pipe carries condensation from your boiler to your outside drain. During extremely cold weather the condensation in this pipe may freeze and cause a blockage causing the condensate to 'back up' into the boiler and cause a shutdown.

Signs that the condensate pipe may have frozen include your boiler's display showing a 'fault code' or warning light as well as gurgling or bubbling sounds coming from the boiler or the condensate pipe.

If you suspect this is the problem, our handy guide on how to defrost a condensate pipe should get your boiler working again in no time.

Still need help?

For a full list of advice topics, see our article on gas central heating problems. If the problem isn't resolved by the advice above, or you'd rather not tackle it yourself, you should enlist the services of a qualified boiler engineer.

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