Is my radiator fan going bad?

What is your question?

my radiator fan started working extremely loud. it worked well in the past but all of a sudden once the AC is turned on the fan spins very very loud. Louder than it used to and it sounds like a diesel engine truck. The AC works fine and car drives normal but the loudness of the fan is not how it used to be, once the AC is turned off then it gradually slows down. The engine idle sound stays normal but only the loudness of the fan has changed. i did drive in an area where volcano ash was in the air slightly before this started happening.

What makes this problem better or worse?

not using the AC

How long has your 2016 Mercedes-Benz GLC300 had this problem?

3 weeks