One problem related to defogger controls has been reported for the 1996 GMC Safari. The most recently reported issues are listed below.
Intake manifold gasket - needed replaced with less than 70k miles on van. Heater fan dashboard switch - when set on floor heat only, it blows out both at the defroster and the floor. Windshield wiper motor - after it stopped working, we grounded the motor and it started working again - now it works intermittently, but not when you usually need it most. Driver's side window motor - failed and required replacement. Air conditioning tube - became brittle and broke - repaired it and the a/c works correctly again.