One problem related to defogger has been reported for the 1997 Mercedes Benz C280. The most recently reported issues are listed below.
Interior windshield fogs once consumer exit the vehicle. The problem occurred after the vehicle was in the park position with the engine off. The visibility through the windshield would get worse if the defogger was turned on and would not defrost when the windshield fogged up. (model-c 280).