EC switch cannot be turned off

Hi, I hope anyone can help me with my car problem.

The car is a W210 E230 1996. The aircon has the digital display. My problem is that the Aircon's EC switch cannot be turned off.

I know there are tons of things that can go wrong. The owner's manual says that if there is not enough freon gas, the compressor would shut down and thus the EC mode is always engaged. I hope this freon is the problem

To backtrack, This EC switch not turning off happened a month ago. My mechanic changed an EVAPORATOR TEMPERATURE SENSOR located underneath the dashboard. And, luckily, this solved the problem and the compressor engaged and everything was back to normal. I did this again, got a new SENSOR, replaced it, but unfortunately, this time it did not work.

What is now wrong?

Please!!! anyone help me.

To add to this, this happens when the car was at on for at least 35 mins without moving and the aircon turned on