[Solved] Danfoss Thermostatic Radiator Valve Head: Hard to Turn, Disassembly, Cleaning & Lubrication Tips

Good morning

At home on the radiators I have such valves installed

with such a thermostat

The thermostat generally works correctly, but the knob turns very hard. The resistance is so great that when turning the thermostat on "heating" it causes the valve to be unscrewed from the radiator. The device has been working for several years so I thought maybe something got dirty there. Therefore, I have a question: can (and does it make sense) thermostat somehow disassemble, clean and can lubricate? If so, can you reach any manual (illustrative picture) how to disassemble it? Or maybe you need to buy a new thermostat?

I have identical thermostats and a similar problem - the head rotates hard, though not enough to unscrew the valve from the radiator. It was so from the very beginning of using the heads, some of them turned a little lighter, but still too hard. I do not know what the reason is or how to disassemble the head without destroying it.
I am also joining my ex-or-colleague's question.

I have it too. I was able to undress it (it is technically possible without damaging the structure, but it must be carefully folded), cleaned (WD-40) and greased with silicone grease. To be able to disassemble, you need to remove these gears limiting rotation and fixing the point max. and min. (to be able to completely unscrew the sensor from the knob).

I disassembled the head according to the drawing in the user manual. The inner thread of the plastic knob works with the aluminum head thread and there is friction. I applied some silicone-Teflon Naskosil grease to the thread and the head turns clearly lighter. Whether it will be a lasting effect, time will tell.

Where did you find the user manual? There are no materials for such antiquities on Danfoss' websites.

I think I found something: http://en.heating.danfoss.com/PCMPDF/vd32c749_RTD.pdf
https://www.avito.ru/tomsk/remont_i_stroitelstvo/termogolovki_danfoss_rtd_3100_1226172958

And an old thread about replacements: https://www.elektroda.pl/rtvforum/topic1529998.html

I have the original, paper manual, if necessary I can share the photo. Practically the same is on the given Russian link, only a little poor quality.
I managed to remove the cover with my fingers, without using any tools. It is important not to change the toothed ring settings, because we will introduce temperature limits. The cutout in both rings should be under the red spot.

Edition 4.12.2018 (after closing the topic)

However, after a few months I found that the head could rotate even lighter and lubricated both points marked in the picture. The head could be rotated so lightly that it partially returned to its initial position. I had to wipe some grease off the left part of the picture. A compromise had to be found between turning slightly and keeping the set position firmly.

In the end I gathered and dismantled this head. The mechanism is very crude, and it is not surprising that it works with resistance. I greased the thread with Silicon + PTFE grease (I had one) and it is easier, but I'm not entirely satisfied. I think that I will gradually replace thermostats for better ones. Below photos from disassembly:

The thermostat lay on the shelf for a few days, I moved it yesterday and I was surprised how light it turns. I don't know if this grease has "matured" or what. It doesn't matter, it's okay now.

=== Edit 07/07/2018 ====
After closing the topic, Felini wrote at PW:

"It is similar with me, after some time the thermostat began to rotate more easily than immediately after applying the lubricant."