99 XJ A/C only works occasionally

Made a typo in the title and this is concerning a 2000 XJ. My cousin's A/C in his 2000 XJ 4.0L auto 4x4 only seems to work some of the time. It works when you first get in the XJ after it has sat a while and gets pretty cold but then later you notice the air is no longer cold at all. I thought maybe it might be low on R-134a so we picked up a bottle to refill it. Got home and started the process, turned the A/C on and the compressor kicked on heard the clutch engage and the aux fan started spinning. Well it kicked off after a few moments as does mine and every other XJ I have ever worked with. So I stand there waiting and waiting for it to kick back on and after what felt like a little too long it finally kicked back on. It later kicked back off and then never came back on. Tried turning the A/C off completely and then back on and nothing. Turned the XJ off entirely and then back on and nothing. I turned my 97 on and observed my A/C compressor in action and it kicked on right away and would cycle on and off in timed intervals. Did the same thing with my other cousin's 99 XJ (yes we have a family of XJs and I am so proud!) and it was the same as mine cycling on and off in timely intervals. The 2000 XJ with the problem also didn't have the aux fan turning on and off without the compressor so I figured it wasn't a problem with the compressor itself but maybe whatever tells it and the aux fan to kick on.

So does anyone have an idea of where I should start? It has gotten very hot down here now in the south and will only continue to get much hotter so we need to get a handle on this soon!

Id say check your relays...one might be shorting out. Not sure about a 2000, but I think the compressor only kicks on when the system pressure is at a certain point, however if you go to low on freon it wont kick on at all. Might also want to check for leaks. On that note, if your system has a leak, you might as well fix it and take it to a place to have it vacummed out and recharged, otherwise you can have moisture and/or air in the system which can make it alternate blowing cold and warm air.

Have your A/C system checked and tested by a shop. It could be low on refrigerant, have a mis-adjusted air gap on the compressor clutch, or have faulty pressure switches.

In 98 or 99 the ECU was reprogrammed and the e-fan only runs when needed instead of running whenever A/C or defrost in on.

My 99 has the same issues that you are describing. The AC will kick on when the jeep is first started and will be nice and ice cold. After about 10-15 minutes of running the system starts blowing warm/non-AC air.

I have yet to find a solution.

second the clutch - that's what my 99 was.

Here's an article you may find useful.

http://www.askamechanic.info/askamech2/content/view/73/47/

Tim_MN said:

It could be low on refrigerant, have a mis-adjusted air gap on the compressor clutch, or have faulty pressure switches.

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Make that third. Check the gap, and the high pressure switch.

Saudade said:

Check the gap

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Checking the gap and removing the shim is what fixed this very same problem on mine.

gw204 said:

Checking the gap and removing the shim is what fixed this very same problem on mine.

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Can you elaborate more on this? Other than main component names I am not very familiar with the A/C system. I am pretty mechanically inclined and can tackle most issues with a decent amount of information and instruction.