fellas. I have an 87 gt , i too was tired of the smoldering heat, especially days when i couldnt put my top down, like rain. but i found something that seemed too easy. i had been throwing around the idea of the r134a conversion in my head, and thought it would cost alot. and also filling up my car with r12 and seeing where it leaks, fixing it, then filling it up agian. with prices of that around 5.00 a oz, that is unreasonable. i found out that stores like napa(where is got mine), they sell a kit for only like 47.99. its a conversion in a box. i thought this was too easy and too cheap to be for real,
Its not that simple really. You have to evacuate the system if there has been a major leak. That requires a vacuum pump. And its surely gonna take more than 15 min. If the system has not been working for quite some time, the compressor will need replacing. If the old compressor failed the system will need to be flushed or you risk ruining the new one shortly. The system can be charged with nitrogen to locate leaks, much cheaper than refrigerant.