Check the coolant level when your engine is cold first. If it's ok they you likely have a blend door motor issue.
Use this link to find a good shop near you.
https://repairpal.com/repair-shops
Alex
RepairPal Certified shops can diagnose and repair your 2004 Chevrolet Trailblazer. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.