I have a 1990 Volvo 760 GLE. I need to recharge my AC. I'm suspicious it has a leak as the last time I tried the AC did last but a day. I has been suggested that I not use stop leak. Can you please share why, and what alternatives I have to prevent the AC recharge from leaking.

 

Stop Leak is a stop-gap solution. I'm not sure what is in it exactly but more than likely it is a seal rejuvenator meaning it softens hardened seals. If your AC lasted only a day last time you recharged it then it is pretty clear you have a gross leak that needs addressing before you try to recharge it. Since your car is 34 years old the AC system probably needs a lot more work than recharge. You need to find the leak(s), address them properly by replacing the seals/orings, pull a vacuum on the system for 30 min or so to ensure it holds and removes any moisture from the system and only then should you recharge it.