Toyota Repair: air conditioning, r 134 freon, 1991 toyota camry

Question
Hi Ted,
    I own a 1991 toyota camry 4 cylinder with 134,000 miles. My problem is the A/C compressor; when turned on it makes a  bearing noise. When I turn the A/C switch off the noise goes away.  Does this mean the A/C compressor will soon fail? Presently the A/C blows cold air.  What can I do now?  Also, if it does fail would you convert this system from the R-12 to the R134 freon?  What components would you change--A/C compressor, receiver dryer, evaporator, expansion valve, condenser for the R134 conversion? Thanks in advance.  

Answer
Yes it does sound like the compressor may be having an internal failure, when this happens the compressor will send metal/aluminum particles into the rest of the system and can clog up other components, since the a/c is functioning at this time I would stop using it to prevent this from happening, I highly recommend changing over to the R-134 freon since it costs about 1/10th of the R-12, the changeover kit is pretty inexpensive and available at most autoparts stores, my recommendation is to replace the a/c compressor, the receiver drier and convert it to the 134 freon.