One problem related to defogger has been reported for the 1998 Mitsubishi Montero. The most recently reported issues are listed below.
At 55mph a smell of plastic burning was smelled, than a loud sound was heard and looked back and the whole back hatch glass was shattered. I think the think the defroster overheated. It lefted a orange looking spot on the glass where the defroster connected to the glass.