Nissan Repair: A/C, blow off sound, expansion valve

Question
My 96 240 is blowing hot air and when I turn the ac on every few mins if makes a blow off sound. Have been told that it is a bad hi-lo switch but not sure where to find it at on the car any help would be great.and also if I just turn the fan on outside air I just get hot air. Thank you for your time

Answer
Justin,

You are going to need a pressure test of the system to see what is going on.  You probably need a new pressure switch or an expansion valve since you say there is a blow off noise.  Either the system is over charged or one or both of the components I mentioned need to be replaced.  I say this since the system is blowing hot air and the system is bleeding off pressure.  Get it tested with someone that has gauges to check what is going on pressure wise.  Email me back and we'll go from there.