2004 suburban LT 4x4 heater on 24/7?

[skycries57]

Hi guys! 04 Scooby here. Heater is on 24/7 and is still heating even when ac turned on? I did a 4 step fix 8 years ago but forgot..something about reset programming, any ideas? Thank you!

 

[zora]

Programming is typically done if required when a blend door actuator is replaced. Did you check if your system has a defective heater control valve in the feed hose going to the heater core?