So the title says pretty much everything. I have a 99 Cherokee and when I have the A/C turned on the fan will kick on for about 5 seconds then off for about 5 seconds and repeat.
I read that it might be caused by low refrigerant so the other day I filled it up. The cheap gauge that you get with the refrigerant bottles says that it is filled now, but the fan still cycles rapidly.
Also, I went to check it again this morning and was going to fill if needed but the A/C condenser and the lines were frosted up. I'm not sure if that is supposed to be like that, both my last XJ's had non functioning A/C. Of it helps, the weather here is 50's and humid and I had the Jeep running for about 5 minutes before I checked under the hood.

 

The hotter the out side temp gets the longer the fan will run , it is normal .

 

That is a little cold to be checking the functionality of the ac. You would get a better reading when it is in the 70's or warmer. Also, buy yourself a set of gauges from Harbor freight or somewhere, so you can read the high side and low side pressures and get a more accurate reading. Look around online or perhaps purchase a service manual and look for the ac section. There should be a chart that shows what range the pressures should be in at what ambient temperature.

 

Found this. Its the same chart as in my 97 FSM. I assume this is the chart in question?

 

That'd be it.

 

Thanks for the tip. I'll wait 'till it warms up a bit and see how it fairs. It just seemed odd to me the the cycle was so rapid.

 

That can happen when its too cool outside, or if its undercharged. I know my Ranger doesn't have an electric fan, but when it is too cool outside, the compressor will cycle on and off similar to that. I don't know what an XJ will do, mine didn't come with AC lol.

 

A jeep with functional A/C is new to me. Haha.

 

In that table you'll see the general rule-of-thumb that the low-side (inlet port) pressure (in psi) should be approximately 1/2 the outside temperature (in deg F).