TRV stuck closed — radiator always cold

If a TRV is stuck in the closed position, hot water cannot enter the radiator and it stays cold even when the heating is on and other radiators are hot. This usually happens in summer when the TRV has been on its minimum setting for months and the pin has corroded or seized in the down position.

Remove the TRV head (unscrew the large ring nut). Check the pin — if it is not springing up, it is stuck closed. The wax element in the head may also have hardened over summer.

Apply penetrating oil around the base of the pin and leave for 10 minutes. Then try pulling the pin upward with pliers — use gentle, steady upward pressure rather than a sharp jerk.

If the pin lifts freely after treatment, replace the head and turn the TRV to its highest setting (5 or *) to confirm the radiator heats up. Then set to your desired temperature.

If the pin cannot be moved: the valve body is severely seized. As a temporary measure, you can remove the TRV head entirely and manually lift the pin with pliers to open the valve — this will leave the radiator permanently on (no temperature control) but at least heating.

The permanent fix is replacing the TRV body — this requires draining the radiator or fitting service valves. Consider a full replacement TRV at this point (£10–£30 for a new valve and head). Many modern TRVs have better frost resistance to prevent recurrence.