Why is my Audi A4 making a strange noise when I turn on the AC?

I recently noticed that whenever I turn on my AC in my Audi A4, there is a loud, metallic grinding noise coming from the engine. It's never happened before and I'm worried about damaging my car. What could be causing this issue and how can I fix it?

It sounds like your AC compressor might be failing. This is a common issue in older Audi A4 models. You should take it to a trusted mechanic to get it checked out and replaced if necessary. In the meantime, avoid using your AC to prevent further damage.