i have a 99 gmc jimmy slt 4x4 4dr with computer climate control. it has a tendency to switch back and forth between hot and cold air, like most of these trucks apparently do. i have read about the air blend motor swithing back and forth, and yes i have the tell tale clicking noise from behind the glovebox. the problem i am having is that the only door i have found behind my glove box seems to work fine, along with the buttons that switch it between outside and cabin air beneath the fan setting on the dash. so where is this little evil blend motor? the other vacuum line behind the box? wouldn't flushing the heater core be a waste of time because i have that crap in my radiator as well? oh and who was the genius that decided were to put the switch for the seat heater in this thing?