My rear heater is not working and it only blows cold air from the upper vents. Does it have to be on the lower vents for heat? The cable that changes upper to lower vent disconnected from somewhere on the blower and I can't find where it attaches to-anyone have a pic? I flushed the rear core pretty well(I think), moved the hot/cold by hand after pulling the metal cover and still nothing. I know this may be a minor problem, but I'd like a toasty cabin for my little kid. thanks all.