Jeep Repair: 99 jeep grand cherokee laredo v6, jeep grand cherokee laredo, jeep grand cherokee

Question
the other day my jeep started to over heat and the check engine light came on.  i stopped the car and looked it over and everything seemed normal.  last year similar problem happened and the thermostat went out but this time it was different.  i called my buddy who is good with cars and he asked if the ac was on and i said yes.  he told me to first let car cool down then start driving it with ac off and see if the problem still happened.  the car was fine after that.  he said he thinks the compressor is going out and its just being over worked when the ac is on. what do you think.  so basically the car is fine when the ac is off and it over heats when its on.

Answer
compressor  ahh no  sounds like teh fan relay is not working. U have a 4.0L engine right with an electric fan? open the hood turn on the AC the fan should come on with in 10 seconds  after 1 min the fan has not some on then u have a bad fan or the relay for it is bad and get the computer scanned as well.
Live near Atlanta?