Stuck radiator valve – radiator staying cold?
Difficulty: Easy · Time: approx. 20 minutes
The heating is on, the radiator has been bled – and it still stays cold? Then the small valve pin under the thermostat head is very likely stuck. This happens especially often after summer, when the valve hasn't moved for months.
The good news: in most cases you can free the pin yourself in about fifteen minutes – without any water escaping, because the thermostat head is only screwed on. All you need is a pair of pliers, a gentle touch and the right technique.
What you'll need
- Water pump pliers or sturdy combination pliers
- Some penetrating oil or a drop of light machine oil
- A cloth or old towel
- Optional: work gloves
Step by step
- 1
Turn the thermostat head to the highest setting
Turn the thermostat head to setting 5. This relaxes the mechanism inside and makes unscrewing it noticeably easier.
- 2
Unscrew the thermostat head
Loosen the union nut right behind the dial anticlockwise – by hand or carefully with the pliers – and pull the head off. Don't worry: no water can escape here, the head is only attached mechanically.
- 3
Check the valve pin
A small metal pin sticks out about five millimetres under the head. Press it with your finger: it should push in three to four millimetres against a spring and come back on its own. If it stays in or doesn't move at all, it's stuck.
- 4
Free the pin gently
Put a drop of penetrating oil on the pin. Then grip it with the pliers and wiggle it gently back and forth, pulling only very slightly if at all. Never hit the pin with a hammer and never pull hard – it could slip right out and water would escape.
- 5
Keep moving it until it springs back
Press the pin in several times and let it return until it springs back smoothly and evenly. Only then can the valve regulate again and let hot water flow through the radiator.
- 6
Screw the thermostat head back on
Put the head back on at setting 5, tighten the union nut hand-tight and then select your usual setting. After a short while the radiator should finally warm up again.
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Upload a photo →Frequently asked questions
- Why does the valve get stuck right after summer?
- Over summer the valve sits in the same position for months. Small deposits from the heating water settle on the pin, and when you first turn the heating on in autumn it no longer moves. It helps to turn all thermostats fully open and closed once in a while over summer too.
- My thermostat head has no union nut – what now?
- Some manufacturers attach the head with a clamping ring, a bayonet fitting or a small screw on the side. Take a calm look at the fastening or find your model's manual – either way, the head always comes off without force.
- The pin springs back but the radiator still stays cold?
- Then the valve isn't the problem. Bleed the radiator again and check whether the other radiators get warm. If only this one stays cold, the return valve setting or missing hydraulic balancing is often to blame – that's one for the heating engineer.