Despairing - Settings on a shower fitting

Hello everyone,

I am slowly desperate. We moved into a new build for rent a year ago. When we moved in, the heating and hot water were set to the highest level. So naturally, there was nicely hot water at our shower faucet.
After the heating technician explained the heating to us and adjusted it to our needs, the shower no longer got properly hot (only about 32°). So we called our landlord, who sent the plumber over.

Unfortunately, when the plumber adjusted the temperature, the window installers were also here and needed some information. I couldn't look over the plumber’s shoulder and now have no idea where he adjusted what.

Now that winter is over and we have turned the heating down a bit, our shower is again not getting properly hot. The water in the separate bathtub or washbasin is nicely hot, just the shower is not.

We have a Grohe mixing faucet in the shower, see picture.

What do I have to do now to have hot water in the shower again?

Thank you for your help:

Picture of the faucet:


Below that is the Rapido T from Grohe

Is anyone here or is everyone just watching? 61 watching and no one has an idea???

Perhaps the hot water supply valve is not opened enough. This is done behind the cover panel. If I understand correctly, on the faucet one knob sets the temperature and the other knob turns the water on and off. Such a regulator, I believe, has a 38 degrees C marking. It is set, then the water is turned on, and the valves (hot and cold water behind the cover panel) are opened so that on the one hand enough water flows out and on the other hand the 38 degrees is reached. If the heating is turned down now, not enough hot water flows through and the water remains cooler.

In short: the warm-cold water mixing ratio needs to be adjusted.

On other faucets this probably does not become noticeable because the adjustment is made on the faucet and not on the supply valve (usually angle valves).

The thermostats calcify over time and then the ratio is no longer correct...disassemble descaling reassemble...shower

Could it be that he turned down the pressure of the hot water? The plumber lowered the pressure at our kitchen because it was too strong for me. However, the ratio is correct for us. Pressure does not really make a noticeable difference at a showerhead. But tell me: is that limescale on your faucet? You should clean it and dry it after showering - it doesn't look nice.

Hello, thanks already for the answers! That all sounds pretty good. Where exactly do I need to turn in the Rapido?

I would turn the two Allen screws (in the picture Pos1 & Pos2), where I would see Pos1 as for the hot water, or are there fixed rules about what is what?

Regards: