Trv not turning off, but heads are ok (work on other radiators)

[Tonytony]

Hello, we have bulldog trvs on all our radiators but have a problem with 2 of them. The 2 upstairs radiators do not turn off (4 downstairs all work fine). If I switch the trv heads, taking one which works downstairs and putting it on an upstairs radiator it also does not shut off the radiator. So the TRV heads all seem to be okay but for some reason the upstairs radiators cannot be shut off with them.

I can compress the pin manually on the upstairs radiators and that does shut off the radiator. So I can only think the TRV head is not putting enough pressure on the pin to shut off the valve. I have tried lubricating the pin with WD-40.

What I think I would like to do is just get manual caps which can close these upstairs radiator valves, would that work and are the fittings universal (so for example would these fit?? Drayton Radiator Valve Cap White 5 Pack - https://www.NoLinkingToThis/p/drayton-radiator-valve-cap-white-5-pack/5649R?tc=ET6&ds_kid=92700072615374555&ds_rl=1249404&gclid=Cj0KCQiAsoycBhC6ARIsAPPbeLu1iS3x_TQFJi9XY7Z8_7X3KnqZqB9Px4Cpx_JWOENbpXbLlqTIDPAaAvqcEALw_wcB&gclsrc=aw.ds

or any other ideas?

Many thanks

 

[gmartine]

There's another similar thead going on this, if you mean use those caps to close the lockshield at the other end of the rad then yes they will do, make a note of the number of turns if the system is balanced.