One problem related to defogger heater has been reported for the 1999 Ford Explorer. The most recently reported issues are listed below.
Contact owns a 1999 Ford Explorer. The plastic vent inside the heater control assembly broke. This plastic vent regulates where the air will circulate through out the vehicle. Also, it controls the defroster/defogger system. During the winter months it would be difficult to see without the windshield being defrosted. The service dealer stated the entire assembly will need to be replaced, but it has not been determined why the component broke. The manufacturer said that the vehicle was no longer under warranty and not do anything. The manufacturer said that the contact would have to repair the vehicle at his own expense.