My 240D leaks a 12-14oz can of R12 in 4-6 months. When the system is charged, it blows some pretty cold air (38-40F). I charged the system with an A/C acceptable red dye/ sealant. Apparently it is supposed to seal small leaks and if it is too big the dye leaks out so the leak can be seen. No dye under the hood, yet the system has discharged. I assume the leak is inside the cab. I cant pay someone to work on my r 12 system unless it is converted to 134a. Should I try to find the leak or just convert it to 134? What is a ball park figure to convert the system given that all the components are working but has a small leak? Thanks, Steve.

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1981 240D auto
1977 240D manual 300 Turbo swap
1983 300SD
1983 300TD Parts car