Never use any stop leak product in the AC.  It will clog and contaminate it and just about everything will need to be replaced.

Definitely do not use any sealer products in your AC system. You can clog up your AC to the point where every component has to be replaced. (I've seen it happen.) Also if you take your car to a shop to have the AC worked on and sealer damages the shop's equipment you will be liable for that.

1991 Toyota Corolla Wagon

Here's the story: Part of the work done by one shop I trust was to get the a/c retrofitted with 134a from r12. This shop said that the freon was leaking out 2 high pressure switches and because one of the high pressure switches was not available from both toyota and aftermarket sources, the car was given back to me with non working a/c. Ok so I went to a 2nd shop I trust and they said one of the technicians in the other shop left one of the tubes loose, and thats where the freon leaked out. Furthermore, the 2nd shop pressure tested the a/c system and said there were no leaks. Now, the a/c blows ice cold but for how long? Do I have any recourse at the 1st shop where I paid 1900.00 for retrofittted 134a non working a/c? I thought I had a handle on who I could trust, or is this just an honest mistake? I feel like I should have had working a/c when I got the car back. By the way, everything else 1st shop did (and they did a lot) works fine. The car runs, shifts, and drives great. I need an honest opinion as to what to do next. Please help. Thank You Sincerely Yours, Paul J Leboeuf

Well basically whatever the second shop charged you make the first job pay for that and just never go back to the first job. They obviously ripped you off but if it's working I would get the money back that you paid extra

You should ask the owner of the first shop to refund you the money you spent at the second shop.

try some stopleak, that's what i've been told where a perfectly good seal won't stay sealed.