Theres a low pressure switch that cuts the clutch from engaging so that you dont eat up your compressor. Have you put a gauge on the system to see where the charge is at? It may be as simple as a leak somewhere and your system is on strike. I cant recall where its located on your car but should be around the dryer area. Just take a paperclip and disconnect the plug and jump it while the ac control is on. If the system kicks on then your charge is gone and the shitty process of tracking down a leak begins...