my 240sx drops rpm and blows white smoke when using ac????

[speed2049]

when i turn the A.C on it drops rpm and white smoke comes out but the smoke only happens when i turn the A.c on... what could this be..??

[terrible01]

white smoke comes out of where? the A/C vents? if its coming out the a/c vents, obviously it's the evaporator coil causing it. I dont remember the exact causes but there could be moisture in you a/c system or the pcm doesn't know how cold the evap coil is getting and it's freezing it. try having a shop perform an evac and recharge. do these cars have temp probes in the evap coil? if so you might want to check that too.