One problem related to defogger has been reported for the 1996 Mercury Grand Marquis. The most recently reported issues are listed below.
The a/c electronic actuator motor controls the a/c and defroster. The unit failed so that during defrost mode only cold air was available. While traveling the unit failed so that I could not defrost the windshield. This unit should only fail in the failsafe state (provide hot air) or have an manual override for the driver so that he can move the door to get hot air when in defrost during a failure. Dt.