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Diagnosing common boiler problems

In this blog we offer some pointers to help you try and diagnose simple problems with your boiler and central heating system.  These may help you resolve simple issues without the need for a call out but, if you are unsure, just contact us.

Please note that we would always recommend that you obtain advice from a Gas Safe registered engineer, and you should never attempt to dismantle your boiler or to make any alterations to it.

Power supplies

  • Check your power supply is on, as the boiler requires electricity to work.
  • Check that the boiler’s gas supply is on (or, if it is an oil boiler, ensure that you have not run out of oil).
  • Check that your water supply is not frozen. The boiler will not work without a supply of water, and it will not work if the condensate pipe (taking steam to the outside of your property) is frozen.

Re-setting the boiler

  • Look at the boiler to see whether the pilot light has gone out? If the pilot light has gone out you may be able to relight it by following the manufacturer’s instructions. These should be set out in your boiler instruction booklet.
  • Some boilers do not have a pilot light but may have a “de-blocking” button.  You can try pressing this, or refer to your boiler instruction annual for further advice on re-setting the boiler.
  • Make sure that your central heating pressure is set to the manufacturer’s instructions (this is usually one bar).
  • Make sure that your water pressure is adequate.  If this is an issue you will normally be able to see this from the pressure indicator on your boiler.


  • Check that your central heating programmer is on.  If it is, you may also want to try increasing the level on your thermostat, as a boiler will only work if the room temperature is lower than the thermostat setting.
  • If altering the thermostat has no effect on the heating, you may have a faulty or old thermostat.


  • If you have a timer on your central heating controls, make sure that this is working and is set correctly. If altering the timer has no effect on the heating, you may have a faulty timer or it may have run out of batteries or lost its power source.