I was try to get my a/c to work The clutch would not engage I jumped the a/c presser switch click it came on Then off then on So i took it up to 1800rpmit stayed on but it was rattling then it started to smoke the coolents fine How can tell if it the cluch or the compresser?

 

it may be neither. i'm nowhere near being an authority, but if i'm not mistaken, as long as the system is intact, that usually means the system is empty.

 

it would help a great deal if you bothered to mention what year and model ur rx7 i first off.
Also, most of them have a pressure switch to prevent burning up the compressor when the system is below an adequate fill level.
Have you bothered to check if the system is filled??

 

Ive repaired, replaced, refilled lots of a/c systems on cars & trucks in my day.