The compressor on your vehicle probably need to be replaced. This could also be cause by a simple refrigerant leak as well.
If it is your compressor you are looking at around $500 to $1000..
If it is a leak, it will be significantly less.
RepairPal Certified shops can diagnose and repair your 1997 Ford Explorer. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.