I converted an '85 T-15 Jimmy to R134a. I replaced the entire gas loop, including the hard lines, with new parts. I got three years out of it before the compressor locked up. The problem with some conversions is that the compressor oil doesn't like to run uphill and pools in the low spots in the system. Ideally, that low spot is the compressor, but my Jimmy had the compressor in the high spot. I'm sure the compressor just ran out of oil and seized.