To find it:
* Open the door: Look closely at the door jamb (the area where the door connects to the vehicle's body).
* Look for a small switch: It might be a small, rectangular or circular switch, often with wires connected to it. It may be partially hidden behind the rubber weather stripping. You might need a flashlight to see it clearly.
* Check all four doors: The location will be similar on each door.
If you're having trouble locating it, a picture of your specific door jamb would help in identifying its location. Also consulting your owner's manual or searching online for a 1999 Jeep Grand Cherokee door jamb diagram might be beneficial.