Cadillac Repair: AC for 92 Eldorado, r 134 freon, r 12 freon

Question
QUESTION: Hi Autohelp- have 92 eldorado, AC wasn't working.  Non-dealer mechanic said 'system' was outdated to add freon, had to update converter to add freon.  Converter updated, freon added, compressor wouldn't turn on.  Not sure what I should do next, would like to avoid going to dealer at all costs.  Thanks for your help

ANSWER: I do NOT understand what you mean by update converter .

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QUESTION: not sure exactly myself.  basically they updated the freon system so that it can accept the current version of freon that is available today- apparently whatever was in the car was too old to accept the freon that is available today.

Answer
You CANNOT use the newer R-134 freon in this vehicle as the sensors are calibrated for the R-12 freon ONLY and when you try and convert the system the LOW PRESSURE sensor will cause the LOW REFRIGERANT light to illuminate causing a fault code to set in the computer which shuts off the A/C compressor.

You have to use an R-12 substitute freon.