10 Critical Boiler Checks Before Calling an Engineer
If your boiler has stopped working, there are several simple checks you can carry out before arranging an engineer visit. Some boiler problems are caused by power loss, low pressure, incorrect thermostat settings, frozen pipes or a temporary system lockout. Completing the checks below may help you identify the issue quickly and could save you from an unnecessary call-out.
Always put safety first. Do not remove the boiler casing, touch internal components or attempt any gas-related repair yourself. If you smell gas, suspect a carbon monoxide leak, or feel unwell with symptoms such as headaches, dizziness or nausea, leave the property immediately and contact the appropriate emergency service.
1. Check the Gas Supply
Check whether other gas appliances in the property are working, such as the cooker hob or gas fire. If none of the gas appliances are working, the problem may be with the gas supply rather than the boiler itself.
Make sure the gas isolation valve near the boiler has not been accidentally turned off. The handle is normally in line with the pipe when the valve is open. Do not force the valve if it feels stuck.
2. Check the Prepayment Meter
If your property uses a prepayment gas or electricity meter, check that there is enough credit available. The boiler may stop operating when the credit runs out, even if the appliance itself is working correctly.
After adding credit, some meters require you to press a button or follow a reconnection process before the supply becomes active again.
3. Check the Electrical Power
Your boiler requires electricity to operate the controls, pump, fan and ignition system. Check whether the boiler display is illuminated and whether there are any lights showing on the control panel.
Look at your consumer unit or fuse box and check whether the boiler circuit breaker or RCD switch has tripped. If it has, reset it once. If it trips again, leave it switched off and arrange for a qualified engineer or electrician to investigate.
Also check the boiler's fused spur switch, which is often located near the boiler. Make sure it is switched on and that the fuse has not failed.
4. Check the System Pressure
Most sealed heating systems should show a pressure of approximately 1.0 to 1.5 bar when the boiler is cold. You can usually find the pressure gauge on the front of the boiler or on the digital display.
If the pressure is too low, the boiler may refuse to start. Some systems can be repressurised using a filling loop, but only follow the manufacturer's instructions if you are confident using it.
Do not overfill the system. If the pressure repeatedly drops, there may be a leak or another fault that requires professional attention.
5. Check the Thermostat Settings
Turn the room thermostat up to at least 21°C and wait a few minutes to see whether the boiler starts. If the current room temperature is already higher than the thermostat setting, the heating will not switch on.
If you use a wireless thermostat, check the batteries and make sure the thermostat is still communicating with the boiler receiver.
6. Check the Programmer or Timer
A power cut can reset the boiler timer or programmer. Check that the current date and time are correct and that the heating schedule is active.
Try selecting a manual heating or “on” setting to confirm whether the boiler responds. Also check that holiday mode, frost mode or an off schedule has not been activated accidentally.
7. Check the Radiator Valves
Make sure the manual radiator valves and thermostatic radiator valves are open. If all valves are closed, the heating system may not circulate correctly.
Turn at least two or three radiator valves fully open and then test the heating again. Do not force a valve that is stiff or damaged.
8. Check for a Frozen Condensate Pipe
During cold weather, the external condensate pipe can freeze and block the boiler. This is often a white plastic pipe that runs from the boiler to an outside drain.
You may be able to thaw a frozen section by applying warm water or wrapping the pipe with a warm towel. Never use boiling water, a naked flame or a heat gun, as these can damage the pipe and create a safety risk.
9. Record Any Error or Fault Codes
Check the boiler display for flashing letters, numbers or warning symbols. Write down the exact fault code before resetting the boiler or calling an engineer.
The fault code can help identify whether the problem relates to low pressure, ignition failure, overheating, fan faults, circulation issues or another system error.
You can check the boiler user manual for basic guidance, but avoid attempting repairs that require removal of the boiler casing.
10. Reset the Boiler Once
A single reset can sometimes clear a temporary system lockout. Follow the manufacturer's instructions and press or hold the reset button once only.
Wait several minutes after resetting the boiler. If the same fault returns, do not continue resetting it repeatedly, as the boiler may have a fault that requires a qualified engineer.
When You Should Call an Engineer
Contact a qualified heating engineer if the boiler still does not work after completing these checks, if the pressure keeps dropping, if the boiler makes unusual noises, if water is leaking, or if the same fault code repeatedly returns.
You should also arrange professional help if the boiler frequently switches off, produces inconsistent heating or hot water, or if any electrical switch or circuit breaker continues to trip.
Important Gas Safety Warning
Never remove the boiler cover or attempt to repair gas valves, burners, fans, internal wiring or combustion components yourself. Gas appliances should only be inspected or repaired by a suitably qualified Gas Safe registered engineer.
If you smell gas, open doors and windows, avoid using electrical switches, do not smoke or use naked flames, leave the property, and contact the gas emergency service immediately.
Need Professional Boiler Help?
Emergency Angel can help arrange a suitable local professional to investigate boiler faults, heating problems and hot-water failures. When requesting assistance, provide the boiler make and model, the fault code, the current pressure reading and details of the checks you have already completed.