Celica Forums General Discussion Interior 1990 celica gts 2.2l vent controls are not changing the flow.

I've owned my celica for almost 6 years now, and while the car runs like a deam, it has many smaller problems that make it a real issue to drive, especially in the summer (Missing a valve for the a/c and non functioning rear defroster for when it gets humid and fogs up.) But i plan to take it one project at a time. My vent controller has never seemed to actually change the vents flows. It always just blows air through the two dash vents on the driver and passenger and the front defroster. Any advice on how to fix this. Any advice could help.