When I bought my 1987 K5, the previous owner told me he had converted the A/C to R134a. I was unaware of how to validate that at the time, but the A/C was cold and that was all that mattered. Now, 8 years later the A/C isn't cold. I had a recharging kit, but when I went to hook it up, the adapter piece wasn't the same. The kit has a quick lock adapter and the refridgerant tank has a threaded adapter. The sticker still says R-12. Is there any way to tell if it was actually converted? Or did the previous owner just blow smoke up my butt? Any input is greatly appreciated!