my 88 m6 seams to have a weak heater? guage reads 1/2 between colored areas(ie normal) at stop signs heater blows warm,as car moves, air cools off,like fresh air vent open ,but knob is all the way to the left(off position)on outside air vent
also noticed that when close car door(w/all windows and s/r closed) i hear a flip type sound under dash like a door is blowing open or closed?