Hook up a set of AC manifold gauges and see what the low side and high side pressures are. If NOTHING comes out, is your blower motor dead? Switch on dashboard dead? Blower motor resistor dead? AC Relay or fuse blown in one of your boxes?
First check your fuses. It could be the fan or the compressors clutch fuse.
Search Nissan Sentra Questions
Nissan Sentra Experts
Related Models For Sale
Used Cars For Sale