will freeze 12 break an R-12 system i found a guy to do it.

 

no

 

Nope, it's a direct drop in.

It does tend to deteriorate over the years, though, so even if you have a sealed system, it will 'fade away' over time, requiring a refill.

 

freeze 12 is mostly R134a with about 20% R142b. Since its a mixture, if in the future you decide to get the AC serviced at a shop, you may be refused. If you're never going to go to a shop, don't worry about it, it'll work just fine. The stuff to stay away from is Arctic Chill, and Greencool, and the like.