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

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
problem has occured for the past 2 weeks.
(4) Answers
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.
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