As a professional mechanic the thing I would have to say is these kits should not be sold to the public for many different reasons. 1) I as a mechanic am not allowed to dump R12 into the atmosphere, there is a large expense involved with recovery equipment and EPA compliance 2) most do-it-yourself people will do this job on their own and not flush the a/c system and not put a vacuum on it before charging it and then bring it into a shop 6 months later when it doesn't work and complain because the bill to correct their errors is so high

GUYS, THIS IS THE WAY IT WORKS!! My shop rate is $40/hr, if you want to help then it goes to $60, if you played with it first, the rate will be unbearable because I now have to figure out what was done and how to correct it!

There are some things that tooling and experience are required for. Air conditioning is one of them so the job is done correctly.