One problem related to defogger heater has been reported for the 1998 Nissan Sentra. The most recently reported issues are listed below.
The heater core of the radiator failed. Defrost coolant spilled into the passenger side in the front and coolant got into the vent system. We noticed the defect because the windshield would not defrost. According to the dealership, the active ingredient of the coolant is ethylene glycol. When we asked why the coolant would spill into the car and into the vents, the dealership service director informed us that "it is the only place it could go. " the manufacturer took care of the cost of repair of this part. However, we are concerned that the car is designed such that coolant would be leaked into the vents and that there is no mention of this possibility in the vehicle booklet. We are also concerned that people who suffer a similar situation will not be aware that they may be inhaling coolant through the vent system for long periods of time without knowing that they are being exposed to this component.