NISSAN SENTRA A/C problem

you should be more specific about your sentra, what year?

in general, it could be one or more of many things. for a start, try locating all AC related relays under the hood, with a cold engine, start engine, and assuming both fans are running, tap on each relay with the end of a screwdriver, one relay at a time, to see if the AC fan stops running.

if this causes AC fan to stop running, look at AC compressor to see if compressor is not running (not just the clutch, i mean the compressor).

if AC fan and compressor are not running after a specific relay is interrogated, replace that relay.