I have a 92 SE and when the weather is mild the AC compressor comes on and will not cycle on and off....it just stays on when the button on the dash is on.....so it wont cycle.....it does get cold.....now ifs its sort of hot outside it wont even come on at all.....so i push the button, it comes on for a split second, turns off, and wont cycle back on.....so cold outside...compressor always on...hot outside...never on.....not sure what to do....

Matt

 

I'd suggest taking it to a nissan dealer or competent A/C service place.
it could simply need to have the coolant recharged, but you could also have a small leak somewhere or problems with your A/C compressor.
good luck