Which line is the high pressure line on the air conditioner cooling system of an Oldsmobile Cutlass 89?

To answer your question followthe lines running into the backof the ac pump. Now the line that runs from it to the condenserwhich is the radiator lookingthing in front of the cars engineradiator, is the high side line.The other line goes to the receiver dryer is the low side.

The line going 2 the (TOP) of the Condenser-{wich is theunit INFRONT of the Radiator}{that has fins on it like the Radiator THE small lines are usally the high pressure lines.JUST trace the TOP (from the condenser)line back 2 the COMPRESSOR & that fitting will b your HIGH side.