Well i checked with a guage I had and it indecated that i was a little low. So i bought a can an filled it up but now the air isnt cold at all!!!!! Lines to the accumulator used to frost over but after the accumlutaor they were just a little cold. Now the lines to the acc are just a little chilled and after it the lines arent cool at all. I was worried that there might be a problem with the acc, looks like ill have to replace that too.
Weebur do you know where the orifice tube is on the '99? If im ripping it apart i might as well replace that too.
Mine is located in the line that runs from the condenser to the evaporator. My original fixed orifice tube was replacable (about $25 for a premium one), later, when I had to remove the original line during my quest for a perfect system it kinked. I had to buy a new line (~$40) and the replacement one had the fixed orifice tube further down the line and it's not removable.
Leave the plastic caps that will come with the new accumulator on until you're ready to add oil and hook it up. Use Q-Tips soaked with PAG100 oil to clean out the females ends of the lines and the "new" O-rings on the male ends. Also leave the cap on the oil container on at all times between cleaning the lines and adding oil to the accumulator.
97-99 Cherokees use about 20oz of refrigerant (don't think putting any more that that will make it run cooler...it won't). An overcharged system can have the same symptoms as a system that is under charged. And, having an overcharged system is hard on everything, especially the compressor.
You'll need to add 4oz of PAG100 oil to the new accumulator. Your system require about 8oz of oil (total). Having too much oil in the system will make it ineffcient and too little can damage the compressor. Pick up a very small funnel to add the oil.
Doing this kind of work is doable, if you take your time and do it right the first time. When you're done you MUST have the system evacuated with a vacuum pump and depending on your altitude your system should be under vacuum of 26-29in/Hg for about an hour. This has to be done through a set of manifold gauges. Then you should turn off the pump and close both the low and high side valves on the manifold gauge and let the system stand for about five minutes. If the vacuum doesn't drop for five minutes the continue evacuating for ten more minutes. Now you're ready to charge the system.
As a side note: The vacuum lowers the boiling point of any water in the system and turns it into vapor and then sucks it out. When you're sure your system is tight then add 20oz of R134a. Doing it the absolute right way would include replacing both Schrader valves and flushing the evaporator and condenser...but you should be OK.
Unless you have a pump and gauges I suggest that once your system is hooked up you take it to an AC shop and have them evacuate and charge your system.