I have the same question as the OP.

the car: 1993 w124 which is running on R-134a refrigerant.

the AC is still kinda cold, but probably not as cold as it was 3 yrs ago, i noticed a difference/decline in the cooling last summer.

Here is a video of the AC dryer window, after a short trip during which i had the AC on:
W124 AC DRIER WINDOW - YouTube

At the start of the video if you listen closely you can hear the auxiliary fans running at low speed, they continue to run until the 32 second mark in the video, a few seconds before the fans shut off, the AC drier window clears up completely, and remains clear until around the 39 second mark in the video, when you can hear the AC compressor reengage along with the auxiliary fans.

a couple of questions:
1)from 1-32 seconds & 40-1:01 are those what the previous posters referred to as bubbles? does this indicate that the system is low on refrigerant?

2) if i continue to use the AC, is there a chance that i can cause damage to the AC system?

3) would an evacuation and recharge be necessary ?

any suggestions or good info would be appreciated

thanks