Hi, my AC hasn't worked since I got my 96 Grand Cherokee a little over a year ago. With the temps consistantly being in the 90's lately I finally decided I would recharge the system (previous owner had told me it just had lost its charge). So I read a couple posts out here on how to do it and such. Last night I went and got a gauge and a couple of R-134a cans. I believe I found the Low side nozzle, in the upper passenger side of the engine compartment with a black cap on it (nozzle located facing up and in the upper left corner of compartment if standing at front bumper). I took the gauge to get a reading prior to connecting a can (directions advised on this as well) Pressure given back was zero. SO I Undid the gauge, screwed the can onto it, and then reinserted onto the nozzle and pulled the trigger. Sprayed about a half a can and wanted to get a reading so I released the trigger. The gauge then went though the green, blue, and yellow zone and was approaching the Red zone on the gauge, which is 65 and WARNING. My air never got cold and since it was hitting the extreme danger warning I ceased this job. What I did notice is that when I had the gauge hooked up the pressure would go up to the Red Warning Line and then the compressor would kick on for a second and the pressure would drop down to zero, then it would raise all the way up to the red warning line, compressor kicks on for a few spins and the pressure drops, this cycle is happening over and over???? Did I have the wrong nozzle? Is there something else wrong? THanks for helping!

Oh yeah its a I6 4.0

Need to re-read those posts a little more carefully. When the compressor isn't running, the pressures will go high on the low side. Static pressure (compressor not running) will be over 100 PSI.

it sounds like you are doing it right.the compressor is kicking on and off because the refrigerant level is still low.your jeep should take close to 2 lbs. of r134.when its properly charged, the compressor wont cycle like that and the suction line going from the evaporator to the compressor will get pretty cold

XJ31 you were right on, I continued to fill and the compressor started kicking on longer and longer until it constantly ran. My uncle explained to me the low pressure switch and how it saves the compressor from burning itself out when theres not enough freon. I filled it up with 2.5 (with leak sealer) cans and had some ice cold air........for about 7 days and now it is back to being empty. I read some posts on dyes you can put in to find the leak, where can I get these, and how does it work? Where are most leaks and are they easy to fix?
Thanks for all your excellent help!

I'd check the stuff you put in, it *may* have dye in it.
With a leak that fast it should be fairly easy to spot. Mine was the high-side hose. Just hope that it's not the part (condenser, evaporator??) that's buried in the dash, that one's a mofo to replace..