I have a 98 buick park avenue, the a/c compressor is not working,but if I jump the compressor clutch relay wire at the computer the compressor kicks in and it blows cold air.

If you buy a shop manual at the local parts house they have all the codes and what they mean. The book is cheap.

just chagre the system would be better if you had it checked for leaks after repair or no repair needed then have an a/c service

if the system doesn't have enough pressure in it, the sensor won't let the AC run.