One problem related to defogger has been reported for the 1997 Jeep Grand Cherokee. The most recently reported issues are listed below.
I have a 97 Jeep Grand Cherokee and it doesn't change from heat to defrost or other setting. It appears that the blend doors on the main heater bay are the problem and I also have checked online and find this a common problem and quite expensive to repair. This created a very dangerous situation while driving in a snow storm and not having the vehicle keep up to the demand on the windshield. I was traveling with my 3 young children and the potential for serious injury was high. It also appears that Jeep is aware of the situation and isn't willing to fix the problem. Potential death and serious injury are great and this is poor judgment for public safety.