R4 versus R12 AC
You may be a little confused. The R4 refers to the type of AC comp. on your friends 300D."R"is for rotary and I believe 4 refers to the no. of cylinders. If you replace the compressor you should replace the reciever/drier to make your warranty on the comp. good. You can get the R-134 conversion kits from Auto Zone for $39.95. It includes all you will need plus three cans of R134. I have converted two of my MBs using the kits, and rebuilt comp. Compressor cost $99.95. Good luck and keep us posted on your progress.
Bill Lewallen Lexington,Ky.