Hi, I have a Volvo 1990 760 GLE. The air conditioning needs a recharge and stop leak. Do I need R134 or R12?

 

Most likely your car needs R12 but look for a sticker under the hood or in the door jamb. 1993 was when R134 started to be used. R12 is very hard to find and is very expensive so you'd want a pro to fix the leak first and consider updating all the seals. You can also google for an R134 conversion kit which would include a new compression, expansion valve, fittings, seals etc.