What to do if…
your thermostat screen goes blank or shows an error and your heating or cooling won’t start

What to do now

1. Rule out gas or carbon monoxide danger first.

   • If you smell gas, do not use electrical switches, do not smoke or use naked flames, open doors and windows if you can do that safely, leave the building, then call the gas emergency number from outside: 0800 111 999 in England, Scotland or Wales; 0800 002 001 in Northern Ireland.
   • If a carbon monoxide alarm sounds, or people feel suddenly unwell indoors, move everyone into fresh air. If you can safely stop using the suspected heating source or appliance without delaying leaving, do that. Keep it off until it has been checked.
   • If a gas appliance may be involved in suspected carbon monoxide, call the gas emergency number for your area from outside.
   • If anyone has severe breathlessness, chest pain, collapse, sudden confusion, or loss of consciousness, call 999. For less severe possible carbon monoxide symptoms, seek urgent medical advice.

2. Check the thermostat’s own power.

   • If it uses batteries, replace them with fresh batteries of the correct type.
   • If it docks onto a wall plate, press it gently back onto the base so it is fully seated.
   • If it is a smart thermostat, check that its receiver, hub, or bridge has power and has not been switched off at the socket.

3. Check the heating or cooling system has power, without opening covers.

   • Check the consumer unit or fuse box for a tripped breaker.
   • Check any nearby boiler, heat pump, indoor unit, receiver, or fused spur switch that may have been turned off.
   • If there is a programmer or timer, check it is not set to off, frost-only, or holiday mode, and that it should be calling for heating or cooling now.

4. Capture the error before changing more settings.

   • Take a photo of the thermostat screen, including any code, message, low-battery symbol, wireless symbol, or warning light.
   • If the boiler, heat pump, receiver, or indoor unit has a visible fault code on an external display, take a photo without removing any covers.

5. Try one clean restart only.

   • After replacing batteries or restoring power, wait a few minutes for the thermostat, receiver, or smart hub to restart and reconnect.
   • If your boiler has a normal user reset button and you know where it is, press it once. If the fault comes back, stop and escalate.
   • If a breaker trips again, leave it off and get qualified help.

6. Get the right help if it does not recover.

   • If a gas boiler or gas appliance is involved, use or check a Gas Safe registered business or engineer for that type of appliance.
   • If you rent, report the fault promptly to your landlord, letting agent, housing provider, or emergency repairs line. Say whether heating or hot water is not working and send the photos of any codes.
   • If you have communal or district heating, contact building management, concierge, the landlord, or the heat network contact, because the fault may be outside your home.
   • If you use a heat pump or air conditioning system, contact the installer, manufacturer support, landlord, or a qualified heating and cooling engineer if power and simple controls do not restore it.

7. Keep the situation stable while you wait.

   • In cold weather, keep to one room, close internal doors, use layers and blankets, and keep vents clear.
   • In hot weather, use shade, safe ventilation, and one cooler room where possible.
   • Keep babies, older people, disabled people, and anyone unwell away from the coldest or hottest room if you can.