When heat is not working in the house, start with the thermostat and the system’s power supply, then check for blocked filters or vents. A thermostat set to the wrong mode, a heating schedule that has changed, or restricted airflow can make a working system seem broken. If those simple checks do not help, the cause may be a fault that needs a qualified technician. The safest next step depends on the type of heating you have: a heat pump, ducted furnace, boiler and electric heaters each have different controls and warning signs. This guide helps you check what is safe to inspect and recognise when to stop.
Before adjusting the heating equipment, note what is happening. Is there no heat anywhere, or is one room cold? Does the system make its usual sound? Is there an error message, warning light or unusual smell? These details can help you distinguish a settings or airflow problem from a system fault.
Do not remove equipment panels, touch electrical wiring or dismantle a heating unit to investigate. Those jobs can expose live components or gas connections and are better left to a qualified technician.
A heating system can be running while some rooms stay cold. In a ducted system, a clogged filter, obstructed return grille or blocked supply vent can reduce airflow. For a wall-mounted heat pump, dust on the indoor unit’s filter can also restrict air. Clean or replace filters only in the way described in the equipment manual; some filters are washable, while others need replacement.
Keep supply vents and return grilles clear. Closing vents in unused rooms may seem like an easy way to direct warmth elsewhere, but it can interfere with airflow in some ducted systems. If you are unsure how your system is designed, leave the vents open and ask a heating professional before changing the balance.
If only one room is cold, compare it with nearby rooms. Look for a blocked vent, a closed radiator valve, a thermostat located in a warmer area, or a room sensor that may be influencing the system. Draughts and poor insulation can also make a room feel cold even when the heating is operating. These are comfort issues worth addressing, but they do not necessarily mean the heating unit has failed.
For a heat pump, confirm that the controller is set to Heat and that the target temperature is above the room temperature. Check the remote or wall controller for a timer, schedule, economy setting or error code. If the unit has a filter that the owner can clean, follow the manual and make sure it is dry and correctly refitted before restarting the unit.
Check that the outdoor unit is not obstructed by leaves, stored items or other debris. Keep clear of the fan and internal components. In cold conditions, a heat pump may pause or change its operation briefly while it manages frost on the outdoor coil. Do not chip ice away or pour hot water on the unit. Persistent heavy icing, repeated shutdowns, an error code or no heat after the basic checks calls for professional attention.
Some heat pumps do not blow hot air as forcefully as a fuel-burning furnace, so the air can feel less warm to the hand even when the system is heating the room. Judge performance by whether the room is gradually warming, not by touching the outlet air. If the indoor temperature continues to fall or the unit stops operating, record any displayed code and contact a technician.
Check the thermostat, power supply and filter first. If the furnace has an accessible status display, note any code or warning light rather than trying to bypass it. A furnace that repeatedly starts and stops, produces unusual noises, or shuts down after an attempted reset needs assessment. Do not remove its cover or attempt repairs to a burner, ignition system or gas connection.
Check that the thermostat is calling for heat and that the boiler’s accessible controls are set as usual. If some radiators are warm and others are not, the issue may be local to a radiator or the heating circuit rather than a complete boiler failure. A pressure gauge, if fitted, should be compared with the instructions for that particular system. There is no single pressure target that applies to every boiler, so do not add water or adjust valves unless you understand the procedure for your model.
If the boiler displays a fault, loses pressure repeatedly or makes unfamiliar noises, note the details and contact a qualified heating professional. Avoid opening the casing or trying to relight a pilot unless the manufacturer’s instructions specifically describe a safe user procedure for your appliance.
For a fixed electric heater, check its thermostat and any accessible power switch. If it has no power, look at the relevant breaker once, but do not keep resetting a breaker that trips again. Never open the heater or attempt to repair its wiring. For a portable heater, check that its controls are set correctly and follow the manufacturer’s instructions for placement and use.
| What you notice | Possible cause | Safe check | Next step |
|---|---|---|---|
| No heat anywhere | Thermostat setting, power interruption or system fault | Check mode, setpoint, display and accessible breaker | Arrange service if basic checks do not restore heat |
| Weak airflow from several vents | Dirty filter or blocked return or supply air path | Inspect the filter and clear visible obstructions | Request help if airflow stays poor or the system overheats or stops |
| One room stays cold | Blocked vent, local radiator issue, sensor placement or heat loss | Check the room’s vent or radiator controls and compare nearby rooms | Ask a professional to assess persistent uneven heating |
| Heat pump shows an error or remains heavily iced | Possible operating fault or defrost problem | Record the code and check for visible obstructions without touching the unit | Contact a heat-pump technician |
| Breaker trips again after reset | Possible electrical fault or overloaded circuit | Do not reset it again | Leave the circuit off and arrange qualified service |
Stop and contact a qualified professional if the system continues to fail after the basic checks, repeatedly trips a breaker, displays a persistent fault, leaks water, or makes a new or concerning noise. When you call, describe the type of system, what the thermostat shows, which rooms are affected and what you have already checked. A photo of an error code can be useful, but do not open the equipment to find one.
Take a different approach if you smell gas or suspect a fuel leak. Do not operate switches, use a flame or try to locate the leak. Leave the area and contact the relevant gas emergency service or emergency services from a safe location. If a fuel-burning appliance is involved and a carbon monoxide alarm sounds, leave the home and seek emergency assistance; do not re-enter until it has been declared safe.
If you rent, report the loss of heating to your landlord or property manager and avoid making repairs or adjustments beyond normal user controls. If the home is becoming uncomfortably cold while the repair is arranged, use only a heater designed for indoor use and follow its instructions. Keep it clear of anything that could catch fire, and never use an outdoor heater or an oven to warm a room.
This checklist can narrow down the problem; it cannot confirm that a component is safe or working properly. If the house remains cold after these checks, arrange a service visit instead of repeatedly cycling the system.
The thermostat may be set to the wrong mode, following a schedule that lowers the temperature, or unable to communicate with the heating system. A power interruption, restricted airflow or equipment fault can also stop heat from reaching the rooms. Check the mode and schedule first, then look for a system warning or error code.
Follow the manufacturer’s instructions if they describe a user reset, and try it only once. If the system shuts down again, a breaker trips, or a fault message returns, stop and arrange service. Repeated resets can mask a problem without fixing its cause.
At startup, the air may not feel as hot as air from some other heating systems, and the unit may briefly pause during a defrost cycle. Check whether the room is warming over time and look for an error code or persistent shutdown. If the temperature falls or the behaviour continues, contact a heat-pump technician.
A dirty filter can restrict airflow and reduce heating performance in systems that use filters, including many ducted systems and heat pumps. Check and clean or replace only filters intended for routine user maintenance, following the equipment instructions. A filter is not the explanation for every heating failure, so seek service if the problem remains.
It can provide temporary warmth if it is designed for indoor use and operated exactly as its manufacturer directs. Keep it away from combustible materials and never use an outdoor heater or an oven as a room-heating substitute. If the central system has a gas smell, carbon monoxide alarm or electrical warning, leave the area and address that hazard first.
When heat is not working in the house, the best first moves are simple: verify the thermostat, check power safely and clear obvious airflow restrictions. If those checks do not restore warmth—or you find a repeated fault, gas smell, alarm or breaker problem—stop troubleshooting and arrange qualified help.
