Radiator Thermostat Not Responding – What to Do?

The most common cause is a stuck thermostat pin beneath the valve head, especially after a period of summer inactivity. Step 1: Remove the thermostat head (usually by turning it anticlockwise or pressing a small tab). Step 2: Underneath you will see a small metal pin – press it in several times using a pen and allow it to spring back out again. Step 3: Reattach the head and test whether the radiator now responds. If the pin cannot be moved at all, the valve is likely scaled up or faulty and should be replaced with a new thermostatic valve (cost approx. £5–15; self-installation is possible following the manufacturer's instructions).