Radiator / heating symptoms / radiator control
Why is one radiator not heating?
Start with the observable symptom. This page explains possible causes; it is not a diagnosis.
If one radiator stays cold while others heat, check its controls and whether air is trapped before assuming the boiler has failed. A stuck valve, imbalance, blockage or local pipe problem may need an engineer.
Start with the pattern.
One radiator is cold or barely warm while the rest of the heating system works.
Possible causes, not a diagnosis.
- A thermostatic or lockshield valve is closed or stuck.
- Air, sludge or a local restriction is affecting the radiator.
- The system may need balancing or the thermostat may be satisfied elsewhere.
Check what is safe to observe.
- 01
Check the thermostatic valve is turned up and the other valve has not been closed.
- 02
Make sure the radiator is not blocked by furniture or a cover.
- 03
Compare pipe temperatures and listen for air, without dismantling valves.
Take the smallest useful step.
- Adjust only the normal user controls and allow time for the radiator to respond.
- Bleed it only when cool and only if the symptoms suggest trapped air.
- Record whether the fault follows the radiator or the room controls.
- Do not force a stuck valve or remove pipework.
- Do not open the boiler casing or alter safety controls.
- Use a qualified heating engineer when a valve is stuck, a pipe is cold or the fault persists.
- Report the issue to your landlord or housing provider if the heating is included in the tenancy.
Professional requirements and rental responsibilities vary by location. Use the qualified local professional or housing authority that applies where you live.
UK example: Gas Safe RegisterWhy this page says that.
This page separates an observable symptom from possible causes and keeps the recommended action within a safe household boundary.