Pontiac Repair: 1998 grand prix heat/ac blower, vacuum source, vacuum leak

Question
The blower does not change from the floor to the other vents or to the defrost.  The fan controls work but the knob that sets the location does not.

Answer
Hi Erwin:

the switching of the modes is done by vacuum. either the vacuum source to the back of the control head has a leak in it between the head and the engine or the control that directs the vacuum to the different modes is bad or possably the mode actuator or linkage is bad for the mode door. with out seeing it it's hard to say. The most likely cause is a vacuum leak between the engine and the control head. good luck :}