2004 GMC Yukon Denali Q&A

2004 GMC Yukon Denali Question: the air or heat only blows out of the defrost no matter what control is set on.

problem has occured for the past 2 weeks. -
Answer 1
Vacuum leak under hood pass. side near firewall. -
Answer 2
maybe your blend door is broken -
Answer 3
You have lost your vacuum to the control head. You most likely have a bad control head. Defrost is controlled by vacuum not a blend door. -
Answer 4
all three are good answers -