"Where do you add r-134a to a 1997 pontiac trans sport"@en . "I am a novice auto worker, but have added my share of 134a to my ac unit, prior to changing the compressor. The \"low pressure\" connector is locatred just behind the radiator fan, on an aluminium tube. Typically it has a small black cap. you connect the 134a refrigerant to that connector. It will take about 4 cans of refrigerant to fill it from empty. If the leaking becomes more frequent, you may need to replace the ac compressor - that will cost you $300 for the part and half an afternoon - or pay a shop $1200"@en . . "I am a novice auto worker, but have added my share of 134a to my ac unit, prior to changing the compressor. The \"low pressure\" connector is locatred just behind the radiator fan, on an aluminium tube. Typically it has a small black cap. you connect the 134a refrigerant to that connector. It will take about 4 cans of refrigerant to fill it from empty. If the leaking becomes more frequent, you may need to replace the ac compressor - that will cost you $300 for the part and half an afternoon - or pay a shop $1200"@en . .