symptoms. With the capsule removed. you should be able to push the pin
down against a spring - and it should pop up again when released. If it
doesn't do this, get a couple of small hammers and simultaneously tap
both sides of the valve lightly to see whether you can free it.


They all move down ok, and come up if pressure is removed, suggesting a
spring is used.

Try actually pulling the pin up, I had a problem with thermostatic valves
sticking when we first moved into our current house. I put it down to the
valves not being used for the year the house was empty. After pulling them
up and pushing them back down a few times, plus a bit of WD40 they all
worked OK. One did leak but only when the pin was part way up, it had to be
replaced of course because in normal use it is often part way up.

Mike