Cadillac Repair: Air Conditioning 1991 Cad Sedan Deville, ac systems, freon

Question
QUESTION: What is the easiest way for a novice to identify the low pressure side of the system,i.e. to add r-134 coolant after a conversion? I am concerned I put the adapter on the high pressure side?

ANSWER: What size engine ?

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QUESTION: 4.9 port injection v-8

Answer
The LOW side is back by the firewall on the passengers side.

The HIGH side is up near the front of the vehicle by the headlights.

ALWAYS WEAR EYE PROTECTANT GOGGLES AND LONG SLEEVE SHIRT WHEN WORKING WITH AC SYSTEMS BECAUSE FREON CAN DAMAGE THE SKIN SEVERLY AND IF IT GETS IN YOUR EYES YOU CAN GO BLIND.