ok so i need to know what kind of ac system did a 1990 xj have is it 134a or the older system i have a bottle of 134a and dont know if i can use it ive tested the compresser and it comes on but when i turn the air on all i get is hot air

 

1990 XJ's came with R-12 factory. You need a license to handle R-12 . they make a conversion kit to 134.