Last early November I had my mechanics do the R12 to R134 conversion on our 91 740 Wagon. We get into the springtime and the air conditioning has zero effect. I took it in to the same mechanics and they're telling me that all of the refrigerant leaked out over the winter, and it will cost $770.00 to repair. Apparently the only way they'll warranty the system is to replace everything. What do you brickboarders think of the situation. Many thanks in advance for your sage advice.