It’s one of the most confusing things that can happen in a West London home: you turn on the hot tap, and out pours nice, warm water. Great! But when you crank up the thermostat for the radiators, nothing happens. Your home stays stubbornly cold. If you’re scratching your head over this, you are certainly not alone. While the instinct is often to blame the boiler itself—especially if you rely on a modern unit for your central heating—the real culprit is frequently a smaller component elsewhere in the system. For reliable boiler repairs in Ealing and the surrounding areas, understanding these common issues is the first step toward getting your heat back.
What’s Going On? Common Causes
The beauty of a modern central heating system is its complexity, but that complexity means there are several points of potential failure. If you have hot water but no heating, here are the usual suspects:
- A Sticking Diverter Valve: This is the most common issue for combi boilers. This valve directs hot water either to your taps (domestic hot water) or to your radiators (central heating). If it gets stuck in the hot water position, your taps work, but the radiators get nothing.
- Thermostat or Timer Issues: The simplest fix! Your thermostat or timer may be set incorrectly, or the batteries might be dead. Check that the heating schedule is actually “on.”
- Air Trapped in the System: Pockets of air prevent hot water from circulating efficiently, often leaving radiators partially or completely cold.
- A Faulty Motorised Valve: In conventional (system or regular) boilers, motorised valves control the flow to the heating circuit. If one of these breaks, the boiler is told to fire, but the hot water can’t get where it needs to go.
- Circulation Pump Malfunction: This pump pushes the heated water through the pipes and around the radiators. If it fails, the water stays inside the boiler (or just gets to the taps), leading to no heat circulation.
Your DIY Fixes: What to Check First
Before calling a professional for boiler servicing in Acton or heating repair in Chiswick, run through these simple checks.
1. Check Your Thermostat and Boiler Settings
- Is it set high enough? Make sure the room thermostat is set a few degrees higher than your current room temperature.
- Is the timer correct? Ensure the timer or programmer is definitely set to the “Heating On” mode, not just “Hot Water Only.”
- Combi Users: Double-check your user control panel for the heating temperature setting.
2. Bleed Your Radiators
If some radiators are warm but others are cold—especially at the top—you likely have trapped air.
- Turn off your central heating system.
- Using a radiator key, gently turn the bleed valve (usually a small square or screw on the side) anti-clockwise until you hear a hiss of air.
- Have a rag or towel ready to catch any drops of water. Stop immediately once water starts to trickle out.
- Repeat on all affected radiators.
Pro Tip: After bleeding, check your boiler’s pressure gauge. Releasing air can lower the pressure, and you may need to top it up using the filling loop to maintain the correct $1.0$ to $1.5$ bar.
3. Check for Sludge and System Dirt (A Sign for Professional Help)
If your radiators are cold at the bottom but warm at the top, it often signals a buildup of sludge and debris (known as magnetite). This restricts the flow of water. While bleeding can help with air, chemical cleaning or a powerflush is required to fix sludge, which is definitely a job for a qualified heating engineer specialising in boiler maintenance in West London.
When to Call the Heating Experts
If the simple fixes haven’t worked, the problem is likely one of the internal, complex components that require expert diagnosis and replacement.
The Motorised Valve or Diverter Valve
You might hear a faint clicking or buzzing noise coming from your boiler or the associated pipework when the heating is meant to be on. If the valve fails to switch, the hot water never reaches the radiator circuit. This part needs replacing.
The Circulation Pump
A failing pump might make a loud whirring, humming, or grinding noise when the heat is requested. Sometimes, a professional can free a seized pump shaft, but often, the unit needs replacing.
Blocked Heat Exchanger
In some cases, internal system faults or significant dirt buildup can cause the heat exchanger to struggle to efficiently transfer heat to the central heating circuit. Don’t risk touching complex boiler components yourself. For safety and a reliable fix, always trust a Gas Safe registered engineer. Whether you need urgent boiler repairs in Ealing, a check-up in Kensington, or general heating servicing across the West London area, professional assistance ensures your system is safe and efficient.
If your radiators are still chilly, getting your boiler looked at quickly prevents a small issue from becoming a costly emergency.