Central Heating Not Working? A Step-by-Step Troubleshooting Guide
Central Heating Not Working? A Step-by-Step Troubleshooting Guide
There is nothing worse than waking up to a cold house in the middle of a Wirral winter. Before you call an engineer, there are several things you can safely check yourself. Many heating problems have simple causes that do not require a professional. This guide walks you through the most common issues in order of likelihood.
Things You Can Safely Check Yourself
These checks involve no gas work, no electrical work and no risk. They are the same things a heating engineer checks first when attending a callout, so working through them could save you the cost of a visit.
1. Check the Thermostat
This sounds obvious, but it accounts for a surprising number of callouts.
- **Is it turned on?** Check that the thermostat is set to a temperature higher than the current room temperature. Digital thermostats can be accidentally knocked to a low setting.
- **Are the batteries dead?** Wireless thermostats rely on batteries. If the display is blank or dim, replace the batteries.
- **Is it in the right mode?** Some thermostats have separate modes for heating, cooling and off. Make sure it is set to heating.
- **Is the temperature sensor accurate?** If the thermostat is in direct sunlight, near a radiator or in a draught, it may be reading the wrong temperature. Try turning the set temperature up by 5 degrees to see if the boiler fires.
2. Check the Timer or Programmer
Your heating may simply not be scheduled to run at this time.
- **Check the clock is correct.** After power cuts, older programmers can lose their time setting. If the clock shows the wrong time, your heating will come on at the wrong time.
- **Check the programme.** Review the on and off times. Make sure both heating and hot water are set to come on when you need them.
- **Try override or boost.** Most programmers have a manual override or boost button that turns the heating on for one to two hours regardless of the schedule. Use this to test whether the system fires.
3. Check the Boiler Pressure
This applies to sealed systems (combi and system boilers). Check the pressure gauge on the front of your boiler.
- **Normal pressure:** 1.0 to 1.5 bar (when cold)
- **Too low (below 0.5 bar):** The boiler may lock out and refuse to fire. You need to repressurise the system.
- **Too high (above 2.5 bar):** The pressure relief valve may have discharged. This is less common but can also cause the boiler to lock out.
How to repressurise: Locate the filling loop — a braided silver hose with one or two valves, usually beneath the boiler. Open the valve(s) slowly and watch the pressure gauge rise. Close the valve(s) when it reaches 1.2 to 1.5 bar. The boiler should reset and fire.
If the pressure drops repeatedly, there is a leak somewhere in the system. Top it up for now, but have it investigated.
4. Check for a Frozen Condensate Pipe
If your boiler has stopped working during freezing weather and is showing a fault code, the condensate pipe is the most likely cause. This small plastic pipe carries waste water from the boiler to an outside drain. When it freezes, the boiler cannot clear its exhaust and shuts down.
How to check: Follow the small white or grey plastic pipe from the bottom of the boiler. If it runs to an outside wall and exits to a drain, check whether it feels icy or has visible ice.
How to thaw: Pour warm water (not boiling) over the external section of the pipe. A kettle of warm water or a hot water bottle held against the pipe will usually do the job. Once thawed, reset the boiler.
Prevention: Insulate the external section with waterproof pipe lagging. If your condensate pipe freezes regularly, ask your engineer about rerouting it to an internal drain.
5. Check the Power Supply
- **Is the boiler getting power?** Check that the boiler's power switch is on (usually a spur switch on the wall next to or near the boiler). Check the fuse in the spur.
- **Has a fuse tripped?** Check your consumer unit (fuse board) for any tripped switches. The boiler circuit is usually labelled. Reset it and see if the boiler fires.
- **Is the power light on?** If the boiler display is completely blank, it is not receiving power. Check the fuse, the spur switch and the consumer unit.
6. Bleed Your Radiators
If the boiler is firing but some radiators are cold or have cold patches at the top, trapped air is the likely cause.
How to bleed a radiator:
7. Check the Radiator Valves
Each radiator has two valves. The thermostatic valve (TRV) on one end controls the temperature. The lockshield valve on the other end is used for balancing and should not normally be adjusted.
- **Is the TRV turned up?** A TRV set to zero or the frost symbol will close the valve and prevent hot water from entering the radiator.
- **Is the TRV stuck?** TRVs can seize in the closed position, particularly if they have not been used over summer. Remove the TRV head (it usually unscrews or unclips) and check whether the pin beneath it moves freely. If it is stuck down, tap it gently or use pliers to ease it up. Replace the head once the pin is moving.
Things That Need a Gas Safe Engineer
If you have worked through the checks above and your heating still is not working, the problem likely requires a qualified engineer. Do not attempt any of the following yourself.
Boiler Fault Codes
If your boiler display shows an error code, look it up in the manual or search online. Common codes relate to ignition failure, flame loss, overheating or sensor faults. These all require an engineer.
No Ignition
If you can hear the boiler trying to fire but it clicks repeatedly without igniting, the issue could be a faulty ignition lead, electrode or gas valve. This is gas work and must be done by a Gas Safe registered engineer.
Leaking Boiler
Water dripping from the boiler itself — not from the pipes or valves — indicates a failed internal component such as the heat exchanger or pressure relief valve. Turn off the boiler and call an engineer.
Unusual Smells
If you smell gas near the boiler, turn it off, open windows, leave the property and call the National Gas Emergency line on 0800 111 999. Do not use light switches or electrical appliances.
Persistent Pressure Loss
If the system pressure drops repeatedly after repressurising, there is a leak. This could be in the pipework, a radiator or internally within the boiler. An engineer needs to locate and fix the leak.
Banging, Kettling or Unusual Noises
Loud banging from the boiler or pipework can indicate overheating, a failing pump or severe sludge buildup. These need diagnosis by an engineer.
When to Call for Help
If you have checked the thermostat, timer, pressure, condensate pipe and power supply without finding the problem, it is time to call a heating engineer. Have the boiler make and model ready, along with any fault code displayed. This helps the engineer prepare and may speed up the repair.
For non-emergency situations, booking a daytime appointment during the working week will be significantly cheaper than an emergency evening or weekend callout.