Both fans not working with compressor indicates a problem. Test both fans by wiring them directly to the battery separately. If one fan is fail, replace.

A temperature sensor should also be present with the fan assembly. It may not be working correctly.

There are also relays that provide power to the fans. I am not familiar with replacing them. I have a link to some part numbers for a 2000 Grand Prix fan relay - http://www.rockauto.com/en/catalog/p...fan+relay,3060