This is on a 2004 XJ-8 and I am the orig owner.

Recently the A/C Heater fan quit working. It has Batt + to it and it has a powerful spin when I ground the other side of the plug. When I turn the Climate Control on, the fan will spin monmentarily and then it stops. I have both the JTIS and the shop manual and I don't see anything like a sensor that tells the box that the fan is working.
Anybody seen this?

 

Glendoramike, from the looks of things, you have 1 of 3 issues.
1) the climate control module is not telling the blower control module to activate the blower motor (problem inside the climate control module)
2) the blower control module has failed and is not processing the signal from the climate control module (bad blower control module)
3) the ground wire for the blower control module has come disconnected, not allowing the blower control module to have a complete circuit.

What I would do to figure this all out. I would take a multimeter with the car off and do a resistance check of the black/white wire on the blower control module (pin 1) and make sure that you have a very low resistance (under 2 ohms). If you don't get that, then this is your problem, need to fix this.

Next, turn the ignition switch to the RUN position and put the climate control module in a manual mode and dial the fan up to its max speed. Now, measuring for VDC, put the black lead on the black/white wire and the red lead on the red wire (Pin 3). You should be getting something around 10-12 VDC. If you are getting 0 VDC, then you have a problem either with the climate control module or the wiring between the climate control module and the blower control module. You can repeat this check at the climate control module going to the red wire there (pin 15) and seeing if you get the voltage there. If yes, then you have a wiring problem. If no, climate control module issue.

hope this helps.