air condition

you may have inadvertently unplugged the low pressure switch to the ac when doing the water pump and or disturbed one of the plug in's to the ac compressor, check your fuses of course,then check to see if your getting a voltage signal to the ac compressor when switched on, (also should hear the clutch click when turned on) if the low pressure switch is disconnected the clutch wont engage, find the low pressure switch and check the connection if ok and clutch still does not engage disconnect the switch, install a jumper to the pins and with the system running and turned on, briefly and I mean briefly, jump the pins and see if the ac clutch engages, if so, the sensor is bad and /or it is doing it's job and the freon is low enough it wont engage, maybe cracked a line ect, have gauges put on and checked for leaks.