If there is no suspected gas or carbon-monoxide emergency, note the display, controls and symptoms. Use only the checks described in your own user manual. An unresolved or returning fault needs a diagnosis visit.
Gas smell or suspected carbon monoxide?
Get outside into fresh air and call 0800 111 999 from a safe place. Do not wait for an online booking. Read emergency guidance
Rule out an emergency first.
A gas smell, a carbon-monoxide alarm or a suspected unsafe appliance is not an ordinary “boiler not working” enquiry. Get to safety and follow the emergency guidance. Do not wait for a text reply or an online appointment.
Look at the information already available.
From a normal, safely accessible position, note whether the boiler display is on and photograph any message. Check what the room thermostat or programmer is asking for and whether other outlets have hot water. These observations are useful without taking anything apart.
Use the manual for your exact model.
Pressure ranges, controls and permitted user actions differ. Do not follow a generic instruction to hold a reset button for a fixed time or fill every system to the same number. If the user manual allows a reset, follow that specific instruction; a fault that returns needs investigation, not repeated resetting.
Describe what happened before it stopped.
Mention a recent power cut, work on the heating, a water leak or very cold weather if relevant. Say whether the fault is intermittent, and whether heating, hot water or both are affected. A photograph of the visible model name and error message can help prepare for the appointment.
Choose a repair visit, not a routine service.
A service is planned maintenance. If the boiler is failing to do its job, select diagnosis / repair so that the visit is arranged around that problem. The initial £125 visit includes up to 90 minutes onsite; additional parts, materials and further work are quoted separately.
Useful official guidance
General information does not replace the instructions for your appliance or an inspection of your home.
HSE: gas safety at homeCadent: what to do if you smell gasIdeal Heating: user guides