I have a 1990 Ford F-150 with a 5.0 A/T, the was changed from R12 to 134 in 2000 and it was fine till end of last year, I paid to get it filled back up with freon and it only lasted about 2 weeks blowing cold. So it went from being completly full to almost empty in 2 weeks so it must have a good leak on it. When it was first filled up it ran great, compressor cycled right no problems. Where is the best place to look? O-rings? I just like to know because the truck is in great shape but I would hate to put alot into it. I have been told it could be from $100 to $2000. Thanks for any input.