Free a stuck TRV pin

Free a radiator's stuck TRV pin so it heats again, using simple tools and careful checks.

AB-01Check the radiator and confirm the faultTurn the TRV dial fully up and down and feel for slight resistance and a faint click near the end of its travel. If you feel nothing and the radiator stays cold, the pin inside the valve body has likely stuck shut. This is common after a radiator has sat switched off all summer.

AB-02Turn off the valve and remove the headTurn the TRV head fully clockwise to close it, then unscrew it by hand — it usually just twists off, leaving the valve body and pin exposed. Keep a cloth handy in case a little water weeps out. You don't need to drain the whole system for this job.

1 each · Cloth or rag

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AB-03Check the exposed pinWith the head off, you'll see a small metal pin sticking up from the centre of the valve body. Press it gently with a fingertip — it should move down and spring back. If it doesn't move at all, it's stuck fast, usually from limescale or an old paint film, and needs freeing rather than forcing.

AB-04Free the pin gentlyGrip the pin gently with pliers, or press the flat of an adjustable spanner against its edge, and rock it gently rather than pulling hard. Small movements are safer than one big tug, which can bend or snap the pin. If it still won't shift, tap the side of the valve body lightly with the spanner handle to loosen built-up scale, then try again.

1 each · Pliers

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1 each · Adjustable spanner

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AB-05Lubricate and work it freeSpray a little penetrating oil around the base of the pin and leave it a few minutes to soak in. Work the pin gently up and down with the pliers until it moves freely under light finger pressure. Wipe away any excess oil with a cloth before refitting the head.

1 can · Penetrating oil (e.g. WD-40)

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1 each · Cloth or rag

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AB-06Refit the TRV head and testScrew the TRV head back on by hand, making sure it seats squarely on the valve body. Turn it to your normal setting and check the pin still moves when you adjust the dial. Give the system a few minutes, then feel the radiator to check it's warming up.

AB-07Bleed the radiator if it's still cold at the topIf the bottom warms but the top stays cold, that's trapped air rather than a stuck pin. Use a radiator key to open the bleed valve at the top corner slightly, holding a small container underneath, and close it as soon as water runs out steadily with no hissing.

1 each · Radiator bleed key

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1 each · Small bowl or container

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AB-08Tidy up and check for leaksWipe down the valve and any drips around the bleed point. Check back after 20 minutes to make sure no water is seeping from the valve body or bleed valve. If the radiator still won't heat up, the valve itself may need replacing rather than just the pin.

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