AC not cold enough

[Oreo]

Hi

I'm new to the list and to my 124 model with its KLIMA relay system (my other car is a 123). The AC does not cool enough during the day when temps are in the 90s to 100s.

I thought it might have something to do with the Evaparator Temperature Sensor not allowing a long enough cycle on the compressor. However, the compressor seems to be engaged most of the time. Gas looks OK. What can cause a low cooling output from the compressor? Is there such a thing as a compressor losing compression? Should I replace the Expansion valve and dryer as a routine?

Thanks All!

Oreo
91 E200 124