I have a Goodman Mfg. A/C split unit outside my house. When it is running, it makes a really loud, high-pitched noise. Is this an indication of a problem? I have a home warranty and am wondering if this qualifies for a repair service call through the warranty company.

It could be the outdoor fan motor needs oiling.
If it is not oiled soon it might cause the bearings in the motor to go bad.
You will have to check with the warranty company to see if it is covered. If not and the motor goes bad they will be replacing it.

How old is it

The air conditioner is at least 12 years old