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RADIATOR FAULTS

All Radiators Cold

If every radiator is cold, the fault is usually with the boiler, thermostat, programmer, pump, system pressure, motorised valve or central circulation.

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Turn the heating off and allow the system to cool before bleeding or adjusting radiators

Radiators contain hot pressurised water. Stop if a fitting is seized, leaking heavily or boiler pressure repeatedly drops.

MOST LIKELY CAUSES

Start with these

No heating demand The thermostat or programmer may not be calling for heat.
Boiler fault The boiler may be locked out or showing an error.
Pump not circulating Hot water may not be moving around the system.
Low pressure or valve fault The system may be unable to operate correctly.
◫ Symptom variations Match the exact heat pattern, sound or leak position. ⌄
  • Boiler display is faulted
  • Hot water works but heating does not
  • Pump is silent
  • Pressure is low
  • Pipes near boiler remain cold
✓ Quick checks Simple checks before removing fittings. ⌄
  1. Confirm the heating is on.
  2. Check whether one radiator or the whole system is affected.
  3. Inspect TRV and lockshield positions.
  4. Look for leaks, air and corrosion.
  5. Let the system cool before bleeding.
1 Step 1 — Check controls Turn the heating off and allow the radiator to cool first. ⌄

Confirm schedule, thermostat and smart controls are requesting heat.

2 Step 2 — Check boiler display and pressure Turn the heating off and allow the radiator to cool first. ⌄

Look for error codes and abnormal pressure.

3 Step 3 — Listen for circulation Turn the heating off and allow the radiator to cool first. ⌄

Note whether the pump or motorised valves appear to operate.

⌁ Common causes explained Why radiator faults develop. ⌄

If every radiator is cold, the fault is usually with the boiler, thermostat, programmer, pump, system pressure, motorised valve or central circulation.

⌘ Advanced diagnostics Heating-engineer checks and repair work. ⌄
  • Test thermostat and programmer outputs.
  • Check pump operation.
  • Inspect motorised valves.
  • Verify boiler demand and flow temperature.
▣ Parts that may need replacing Common components linked to this fault. ⌄
  • Circulation pump
  • Room thermostat
  • Programmer
  • Motorised valve
  • Pressure sensor
! When to call a heating engineer Conditions that should end basic troubleshooting. ⌄
  • Boiler pressure keeps dropping.
  • A radiator or valve is leaking heavily.
  • Valves are seized or corroded.
  • Several radiators remain cold.
  • The pump or boiler may be faulty.
? Frequently asked questions Common radiator questions. ⌄

Should I bleed radiators while heating is on?

No. Turn the heating off and allow the system to cool first.

Why did boiler pressure drop?

Releasing air can reduce pressure in a sealed system.