Take your vehicle to a reputable shop and get the sytem evaluated. If they know what they are doing you will probabaly have to spend $ but the problem will be corrected. Insist on a oem expansion vavle, the cheaper aftermarket ones have a high malfunction rate and are not worth the money saved. E28 ac systems are not cheap to work on especially if still charged with R12. The key to AC is to remember "there are no shortcuts to AC repairs" especially if you want it done right. For a shop that is close to you to start the process follow the link.