I recently purchased a 2000 grand Cherokee limited. The AC doesn’t run cold. It has a good fuse, the compressor doesn’t turn on, and adding refrigerant would make it turn on and then off over and over again. Any ideas on what could be wrong with it?
Literally just yesterday fixed this on my wife’s 97 xj. Ac is supposed to be a closed system but sometimes they leak down over a couple years. The problem with just adding more is it’s hard to know how much is still in there and adding too much will also not cool efficiently and could damage the compressor. The best way is to get a set of manifold gauges and a vacuum pump. Evacuate any refrigerant still in the system, turn on the pump and pull a vacuum on both high and low pressure sides. I usually let it run about 30 minutes. Then close the valves between the pump and the gauges. Turn the pump off and wait another 30 minutes to see if vacuum remains. If the vacuum reading drops, you have a leak that must be fixed before proceeding to fill the system. If vacuum holds steady though, unhook the pump and attach your can of refrigerant. The pros charge systems by weight and there should be an under hood label that tells you what the charge should be. Our 97 xj was 1.25 pounds. I had two 12 ounce cans, so about a can and a half. Start the engine, turn the ac to recirc and the fan to max. Open the can tap and slowly open the valve between the can and the LOW pressure side. The vacuum you pulled will now draw the initial charge into the compressor. Watch the gauges so you don’t put too much pressure in all at once. The pressure will rise and then as the compressor kicks on, it will drop again. Try to avoid exceeding 100 psi. The gauges will come with charts showing what the approximate pressure should be for high and low sides. They can vary depending on what the outside weather/temperature is, so read those directions. If the low pressure side rises and stops pumping back down, you are over charging. Bleed a little off the low pressure side to bring the pressure down around 45-50 psi. I put in a can with some leak sealer and dye and then a half can of pure r134a. Not what everyone has to do, just what I did. A few years ago I replaced the compressor on this truck and I originally just used straight r134a. The compressor came pre-filled with oil. Anyway, the ac is blowing frosty cold again. And sometimes the compressors will turn on and off to maintain temperature. They don’t always run continuously so let the air temperature and gauge readings be your guide. Good luck!