Why does my Audi 80 make a loud squealing noise when I turn on the AC?

I recently noticed that whenever I turn on my AC in my Audi 80, there is a loud squealing noise coming from the engine. It doesn't happen when the AC is off or when the car is idling. What could be causing this and how can I fix it?

It's likely that your AC belt is worn out and needs to be replaced. Over time, the rubber can wear down and cause this noise. I recommend taking your car to a mechanic to have the belt inspected and replaced if necessary.

Another possibility is that your AC compressor is failing and causing the noise. This is a more expensive repair, but it's best to have it fixed sooner rather than later to avoid further damage to your car's AC system. Take it to a trusted mechanic for a diagnosis and repair.

Check your AC system's tensioner pulley and make sure it's properly aligned and tight. A loose or misaligned pulley can also cause squeaking noises. If it's not an issue with the pulley, then it's likely one of the other components mentioned by the other answers. Take it to a mechanic for a thorough inspection.