burkett.j

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.

tech

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

Red1992XJ

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.

fb97xj1

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

Red1992XJ

That'd be it.

burkett.j

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.

Red1992XJ

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.

burkett.j

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

jordan96xj

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).