AC PROBLEMS on 1999 Ford Mustang

The AC on my daughters 99 mustang only blows hot air. The compressor works and the coolant is full any suggestions?

2 answers 2 comments
I had the same problem. They changed out a microchip and it was all fixed!
Do you know what the microchip was called?
you need to have the freon checked as well as the pressures. take it to a shop for a bid.

Thank you will try