My 87 560 was converted to r134 by the MB dealer when they replaced the condenser & new drier. It seams to cool OK, especially here in the Midwest. My compressor is a little nosier than I am accustomed to hearing. Is this normal for r134, and does R-12 and mineral oil allow the compressor to operate quieter?

How difficult would it be to convert a unit from R134 back to R-12?

Thanks,

BD

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87 560 SL
93 300E 2.8
91 300CE-24