Replacing shower thermostatic cartridge

[jacoscar]

I’m trying to fix a thermostatic shower. The shop that sold it to me originally provided this part, which is slightly different from the original one.
First photo: original cartridge
Second photo: what the replacement cartridge looks like
Third photo: what is this part?

With the replacement cartridge fitted no water comes out of the shower. Also, I don’t see how this part could affect anything, as it’s just a metal part that slides as the temperature knob is rotated. Do I also need to replace the part from picture 3?

 

[denso13]

Third photo: what is this part?

That's the thermostatic part which goes in the other end of the shower bar. Did the shop sell you both?

 

[jacoscar]

That's the thermostatic part which goes in the other end of the shower bar. Did the shop sell you both?

Yes. They sold me both.
I imagine there is a similar piece inside the shower bar that I failed to remove, I briefly tried with some pliers with it wouldn’t budge.

Do you mean I need to open the shower bar on the opposite side by removing the flow handle?

Also, there was a white plastic bit that stops setting too high a temperature that won’t fit onto the new piece.

 

[denso13]

Yes. They sold me both.
I imagine there is a similar piece inside the shower bar that I failed to remove, I briefly tried with some pliers with it wouldn’t budge.

Do you mean I need to open the shower bar on the opposite side by removing the flow handle?

Also, there was a white plastic bit that stops setting too high a temperature that won’t fit onto the new piece.

One side is the flow control, the other adjusts the temperature. Which one is in your second pic, on the right hand side?

 

[jacoscar]

One side is the flow control, the other adjusts the temperature. Which one is in your second pic, on the right hand side?

That’s the temperature control

 

[denso13]

That’s the temperature control

Then you'll probably need to fit the thermostatic bit as well, to match the spindle bit.

 

[jacoscar]

I’ll try and pull it out. The other bit I’m not clear about is that the adjustment white thing that goes onto the spline shown in picture 1 doesn’t fit on the new part. And it didn’t come with one, so there will be no scalding protection (I cannot set a max temperature)

 

[denso13]

If in doubt just change the whole valve, they are cheap as chips.