Guide · Central heating
When the heating will not come on, or will not go off, the thermostat often gets the blame. Sometimes it is at fault. Just as often, it is the batteries, the timer, a lost wireless connection or the boiler itself. Working through these checks in order usually narrows it down quickly.
Before looking at the thermostat, check the boiler. Is it showing power, an error code or a low pressure reading? If the boiler has locked out, no thermostat will get it going. Our boiler not working guide covers those checks.
Next, check the timer or programmer. If the heating is set to off at that time of day, turning up the thermostat will do nothing. Try switching the heating to 'on' or 'constant' to test.
Many wireless and smart thermostats run on batteries. A blank screen, a flashing battery symbol or a thermostat that responds slowly are all signs they need replacing. Wired thermostats take power from the heating circuit, so a blank wired thermostat may point to a tripped fuse at the boiler's fused spur or a wiring fault.
Set the thermostat a few degrees above the current room temperature and wait a minute or two. You should hear a click from the thermostat or see the boiler fire. If the room is already warmer than the setting, the thermostat is doing exactly what it should and will not call for heat.
A thermostat in a hallway near the front door, in direct sunlight or above a radiator can give misleading readings. One in a cold hall may keep the heating running when the living room is already warm; one in a sunny spot may switch it off too early. If the readings feel wrong, the position may be the issue rather than the thermostat.
Wireless thermostats talk to a receiver near the boiler. If the receiver loses the signal, the heating may not respond. Look at the receiver for a status light. Many have a pairing or reset process in their instructions. Thick walls, metal objects and moving the thermostat further away can all weaken the signal.
Smart thermostats add Wi-Fi and an app, which brings extra things that can go wrong. Check that your home Wi-Fi is working, that the app shows the thermostat as online and that no schedule, holiday mode or away setting is overriding what you want.
If the app has lost connection, the heating may still work from the thermostat or the receiver's manual button. A recent change of broadband router is a common cause, because the thermostat is still looking for the old network.
Nest thermostats rely on the heat link wired near the boiler as well as the thermostat itself. If the display shows an error, the Nest app and support pages explain each code. Common issues include low battery, lost Wi-Fi, the heat link losing power or the boiler's wiring. The same principle applies to Hive and other brands: check the hub or receiver as well as the unit on the wall.
Underfloor heating usually has a thermostat in each zone controlling a valve on the manifold. If one zone stays cold, check that thermostat's batteries and settings first, then whether its actuator on the manifold is responding. Some underfloor thermostats use a floor probe, which can fail. Our underfloor heating page explains how these systems are controlled.
If the thermostat clicks and calls for heat but the radiators stay cold, the fault is elsewhere: a motorised valve, the pump or the boiler. Our hot water but no heating guide covers that situation in more detail.
Older dial thermostats can wear out, and replacement is often simple. If you are replacing it anyway, it may be worth considering a programmable or smart model. Our smart thermostat installation page explains compatibility with different boilers.
If you have worked through these checks and the heating still is not behaving, call or WhatsApp 07429 632804 or use the quote form. Our central heating page covers controls and system faults.
Common questions
Clear answers before you arrange a visit.
Common causes are flat batteries, lost Wi-Fi after a router change, a schedule or away mode overriding your settings, or the receiver near the boiler losing power. Check the app and the receiver as well as the thermostat.
Check its batteries and settings first, then whether the actuator on the manifold for that zone is opening. A failed floor probe or wiring fault can also stop it working.
It depends on the model. Most have a reset or pairing procedure in the instructions. For smart thermostats, the manufacturer's app usually guides you through it.
It can stop the heating coming on, but on a combi the hot water usually still works, because that is controlled separately by the taps.
Usually on an inside wall in a main living area, away from radiators, draughts and direct sunlight, at roughly head height.
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