Jeep Repair: 2000 Jeep Grand Cherokee electric fan problem, jeep grand cherokee, electric cooling fan

Question
The electric cooling fan will not run when vehicle warms up.  The fan is working when the car is first started cold and will not come on again if the vehicle is stopped and restarted.  I have replaced the fan relay with an aftermarket part which did not correct the problem.  The fan works with 12v directly applied.  The problem started after having the oil changed last week.  I just checked the relay (it would appear pin 1 GND, pin 2 cntl, pin 3 fan+, pin 4 12v) and am getting 12v to pin 3 (GN wire) when the fan should be operating (AC on) so it would appear the relay is working properly and the problem is on the GND side of the fan.  Where is the GND wire of the fan motor connected?

Answer
well it wont be the ground connection it self because it shares the ground with 8 other things  one being the ground for the fan relay. IF u apply 12 v to the power side it it still works then its not the ground  u can get an INTERMITTENT PROBLEM operation from a ground wire and it rest when u cycle the key. Tell me more about if u have the jeep running does the jeep over heat when let sit for awhile running? does the fan come one and stay on while the ac is running does the fan slow down b4 it stops?