where is located the low ac pressure switch

100 lbs

That tells me nothing. You need to jumper the a/c compressor relay and tell me the low & high side readings. You will need a a/c manifold gauge set to view the pressures. You should have 30 to 40 PSI on the low side and 250 to 275 on the high side. These readings will show if you have a proper charge in the system.

100 lbs in the low side and the compressor is not working