Thermostat Repair

Work through these before booking a visit. Many faults are cured here:

1. 1

   Is the display blank? Replace the batteries in a wireless thermostat with fresh ones of the right type. A wired thermostat with no display may have lost power, so check the boiler is on and that nothing has tripped at the consumer unit.

2. 2

   Check the setting. Turn the temperature a few degrees above the room temperature. Check the thermostat is not in off, holiday or frost mode, and that the clock is right, especially after a power cut or a clock change.

3. 3

   Check the boiler. Is it powered, showing a fault code, or low on pressure? If the boiler has stopped, the controls cannot start it: see our boiler repair service.

4. 4

   Check the receiver. Wireless thermostats talk to a receiver near the boiler. A warning light or a lost signal light usually means they need pairing again; the manual explains how.

5. 5

   Check the Wi-Fi. For a smart thermostat, check the hub's lights and your router. Restarting the hub often restores the connection.

6. 6

   Listen for a click. When you turn the thermostat up, you should usually hear a click from the receiver or boiler as it calls for heat.

Do not open wired controls, the wiring centre or the boiler casing: they carry mains voltage.

The most common causes are:

• Flat batteries: The most frequent fault with wireless thermostats, often showing as a blank or flickering screen.
• Lost pairing: After a battery change, a power cut or a new router, the thermostat and receiver or hub can lose their link.
• A failed receiver relay: The receiver gets the signal but its switch inside no longer turns the boiler on.
• Wiring faults: Loose terminals, a damaged cable or wiring that was never right after an earlier installation.
• A failed thermostat: A worn mechanical dial, a sensor reading wrongly or an electronic fault.
• The wrong position: A thermostat near a radiator, in sunlight, in a draught or in a kitchen reads the wrong temperature and switches at the wrong time.

Signs that the thermostat itself has failed include:

• The heating does not respond when you turn the thermostat up, but the boiler works for hot water.
• The heating will not turn off, even when the room is well above the setting.
• The temperature shown is clearly different from a separate room thermometer.
• The display is blank or shows errors even with fresh batteries.
• The boiler switches on and off every few minutes.

On a visit, we test whether the thermostat actually switches, whether the receiver passes the signal on, and whether the boiler responds to a call for heat. That tells us which part has failed, so you do not replace a thermostat when the fault is somewhere else.

If the thermostat is calling for heat but nothing happens, the fault is between the thermostat and the radiators:

• Combi boilers: If hot water works but heating does not, the fault is usually the thermostat, receiver or wiring, or the boiler's diverter valve.
• System and regular boilers: Check the programmer is set to heating on, not just hot water. A stuck motorised zone valve or a failed pump stops heating while the boiler still fires; that is a system fault, covered by our central heating system maintenance service.
• Underfloor heating: Room thermostats talk to a wiring centre and actuators at the manifold, covered by our underfloor heating maintenance and repair service.
• One room cold: If the rest of the house is warm, look at the radiator valve; a stuck TRV is a job for our radiator maintenance and repair service.

If the whole house has no heating in cold weather, especially with elderly people, babies or anyone unwell at home, see our emergency heating services.

• Receivers and relays: A failed receiver is replaced and paired with the thermostat. Some thermostats and receivers are sold only as a matched set.
• Wiring faults: Loose or wrong connections at the thermostat, receiver or wiring centre are corrected. The work is tested and certified through one of the routes the building regulations allow. Wider faults, such as circuits tripping, go to our electrical repair services.
• Programmers: A programmer that loses its settings, shows errors or no longer switches is reset or replaced with a compatible unit.
• Positioning: A thermostat in the wrong place can be moved; a wireless thermostat is the easiest to reposition.

If a thermostat has failed, we replace it with a compatible unit, using the existing wiring where possible. Older dial thermostats and programmers are often no longer made, so the replacement may look and work differently; we set it up and show you how to use it. If you want to take the chance to upgrade to a smart thermostat or smart TRVs, that is covered by our installation service.