Central heating: one radiator stays stone-cold but pipe feeding it is really hot. WTH :( <New thermo

[Skii]

Sounds like a similar issue to what we have every year You need to take the Thermostatic valve off the end of the radiator - usually they just twist off (you have to hold the end of the assembly and twist the collar that holds it on to the pipe)



This will reveal a small pin that should be spring loaded, if you are in a hard water area like me these seize up after not being used for 6 months so a gentle tap or two with the end of a hammer or screwdriver should get it moving again.

Replace the plastic valve assembly and you should be good to go

 

[Richie]

My radiators work the other way - the thermo valve is on the water exit side. I have a plain +/- valve at the water intake side so check valves on both sides.

 

[KatanaDV20]

Sounds like a similar issue to what we have every year You need to take the Thermostatic valve off the end of the radiator - usually they just twist off (you have to hold the end of the assembly and twist the collar that holds it on to the pipe)



This will reveal a small pin that should be spring loaded, if you are in a hard water area like me these seize up after not being used for 6 months so a gentle tap or two with the end of a hammer or screwdriver should get it moving again.

Replace the plastic valve assembly and you should be good to go

I did this completely by accident - and you are right it worked brilliantly About 2 hrs ago I was getting annoyed and twisted the valve kinda hard because I was ____d-off with it..and it came away in my hand (just like in the diagram you posted). I was in a panic for a few seconds but when no geyeser of water appeared I calmed down. Thats when I noticed that pin. I gave it a whack with a shoe and in under 10 secs the radiator was/is burning hot!! Thanks for replying!!

 

[deaglecat]

Might be air (if you are lucky).
Might be build up of sludge inside if you are not.

If the top is cold but bottom is hot them probably air.
If the top is hot but a triangle of cold from the bottom then sludge... which is a bigger problem.

 

[dpbadger]

Was going to say pin under TRV but someone beat my to it.

 

[teulk]

****** deleted ****** as you have sorted it