What year is your car? Most of the time someone will label the compressor as 134A or you can usually tell by the quick disconect fittings. Should have a red one and a blue one ( the Caps that is).
Shoot us a pic of the fittings and I can tell you if its 134A or not
Also, another way is that instead of being weak, with 134 your A/C will completely suck
