Air comes out from defrost but not sh. 2002 gmc yukon xl but rear air works fine

What is your question?

A/c blowing cold in rear and hot air from defrost at windshield, no air blowing from dash vents or floor vent on any setting

What makes this problem better or worse?

N/a

How long has your 2015 GMC Yukon XL had this problem?

Just started past week