TRV pin not springing back

[JukeBoxUK]

I have a cold radiator, so I removed the TRV head to see if the pin was stuck. It's not, I can move it back and forth with pliers, but when I push it in it is not springing back.

The TRV head is an old Danfoss RAVL valve which pushes on and is then secured by a compression clip and screw (shown in photo), rather than a screw on head. I had hoped that either unsticking the pin or replacing the TRV head would help (this is the only one I could find which would fit: https://www.amazon.co.uk/gp/product/B000VT4GJQ), but if the pin isn't springing back, I'm guessing this won't help?

My question is, do I need to replace the valve body for a new one (and one which would allow fitting of a more modern screw fit valve head) or is there a way to get the pin to spring back again?

Many thanks

 

[Fred Blogs]

When my danfoss TRV used to stick I tapped the pin gently with a hammer and sprayed WD40 on it it eventually freed itself. If the platform inside the head moves back and fore when the adjuster knob is turned then the head is okay. I changed mine for more modern looking ones that I bought online, google that head there are plenty of pictures to help. I don't think that one you have linked to will fit. If you want the screw on type heads then you will have to change the valve. Of course I suppose the spring could have broken but I have not known that happen. I have lived in two houses now with that type of valve but as I changed all the rads in both houses I also changed the valves to the more modern screw on type

 

[JukeBoxUK]

Thanks for your reply. I think that head I linked to should fit. Here's another image of the same item, showing more detail of the attachment type:

 

[pepsi_max2k]

I have a cold radiator, so I removed the TRV head to see if the pin was stuck. It's not, I can move it back and forth with pliers, but when I push it in it is not springing back.

The TRV head is an old Danfoss RAVL valve which pushes on and is then secured by a compression clip and screw (shown in photo), rather than a screw on head. I had hoped that either unsticking the pin or replacing the TRV head would help (this is the only one I could find which would fit: https://www.amazon.co.uk/gp/product/B000VT4GJQ), but if the pin isn't springing back, I'm guessing this won't help?

My question is, do I need to replace the valve body for a new one (and one which would allow fitting of a more modern screw fit valve head) or is there a way to get the pin to spring back again?

Many thanks
View attachment 336626

So no one answered OP’s question, and I have the same issue - valve stuck with an old Danfoss TRV (neither the pin nor the head are the issue - the pin’s moving freely because the valve / spring is stuck).

OP did you ever fix this? I’m wondering if screwing out the pin insert will allow enough access to poke the valve free without destroying anything or soaking the house.

Also before anyone says replace the whole thing - this specific Danfoss has a union connector and extended length to the (likely) inlet pipe, and probably an odd size connection to tails, which would mean replacing tails, extending pipe work, draining the entire system, probably having to flush out decades of dirt before refilling, possibly even replacing the radiator if it’s rusted enough not to take new tails, new wall brackets… like I wanna tap something with a hammer not get a degree in plumbing

 

[Exedon]

Taping pin gently normal works.
After that if your not confident in dealing with it you don't need a degree in plumbing you just need a plumber!
We would just freeze pipe adapt it then fit new trv few minutes job but we have the gear.

 

[pepsi_max2k]

Heh thanks, will try tappy tapping the valve it to free the washer (pins already moving free but with no spring/resistance). If I get to unscrewing the insert I’ll let you know how it goes.

 

[Biggles..]

if it’s an RA valve, replace the insert, Theyre under a tenner.
Unless you have the danfos or Herz tool, you’ll need to drain down.

 

[pepsi_max2k]

if it’s an RA valve, replace the insert, Theyre under a tenner.
Unless you have the danfos or Herz tool, you’ll need to drain down.

It looks like an older style RA-FN type but a different looking insert so probs incompatible with anything on the market, am yet to find the actual model number for the valve (it’s got 1/208 printed on it, possibly implying 1/2 connectors with 8mm union).

 

[JohnD]

You can exercise the pin up and down by holding a soup spoon in the palm of your hand. This prevents the pin going into your hand, and the curve of the spoon prevents the pin going side ways and bending.

You can clean the pin with the wife's toothbrush and WD40. The pin should be sealed so water can't get out and build up scale

 

[pepsi_max2k]

Again, the pin is fine, it’s moving freely. The washer behind the pin is stuck.

 

[JohnD]

Again, the pin is fine, it’s moving freely. The washer behind the pin is stuck.

Yes, I made the mistake of reading the OP who said "when I push it in it is not springing back."

 

[pepsi_max2k]

Yes, I made the mistake of reading the OP who said "when I push it in it is not springing back."

Actually this is the same issue - it’s moving freely as in we can manually pull it in and out with no resistance.

It doesn’t “spring” back because the washer inside is stuck closed and not pushing the pin back. We can slide it back but they won’t pull the washer back (some other designs may be physically connected to the washer/plug, this may or may not be designed like that - if it is, it’s corroded off and it’s borked, otherwise it’s just the washer / spring is stuck). See pic - 3 is moving, 4/5 is not, this is current ra-fn diagram but best I can find)

Hoping something like this procedure may work but might not risk it unless someone here with identicle valve can confirm it's not gonna fall apart in my hands