minimum conversion--fill system with 134 to chk for leaks. fix leaks. evacuate system. repl receiver-drier and o rings at that connection. vacuum system and recharge with 134a and at least 2 oz of oil.

to do it correctly to last for a long time--fill with 134 to chk for leaks. note pressures on guages. if good, you can reuse compressor if it's not the leak. make note of where leak is. disassemble all hose connections (condensor, compressor, rec-drier, expansion valve, evaporator). flush all lines, remove compressor and turn upside down to drain overnight. reassemble with all new o-rings, new exp valve, new rec-drier, the two switches on the rec-drier. vacuum system and recharge with r12 or 134a and the appropriate oil.

not a bad DIY job if you have a/c gauges and a vacuum pump and know how to use them.

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"the simplest answer is usually the correct answer"

1991 190e, 2.6 (helga)
91,000 mi