Cadillac Repair: 98 Eldorado ac/off low presure side, star engine, atmospheric air

Question
I have a 1998 Eldorado with the north star engine , my A/C
is in the off position an will not turn on by the ac switch due to  low presure switch .Im trying to find out how to unlock it to turn . the compresser on to fill with freon. thank you for your time  ..

Answer
Is the A/C system FULLY EMPTY of freon ?. you will need aset of A/C gages to determine this.

If it IS totally empty you have a leak in the system and this will require:

repairing the leak.

Evacuating all the atmospheric air from the A/C system.

Recharge the system.